Puberty refers to the process of physical changes by which a child's body becomes an adult body capable of reproduction. CHILD syndrome (or congenital hemidysplasia with ichthyosiform erythroderma and limb defects) is a genetic disorder With regard to living things, a body is the integral physical material of an individual For the 2008 British film by Noel Clarke see Adulthood (film. Reproduction is the Biological process by which new individual Organisms are produced Puberty is initiated by hormone signals from the brain to the gonads (the ovaries and testes). Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries. "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of brain, bones, muscle, skin, breasts, and reproductive organs. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the The skin is the outer covering of living tissue of an animal (or plant The breast is the upper Ventral region of an animal’s Torso, particularly that of Mammals including Human beings. A sex organ, or primary sexual characteristic, as narrowly defined is any of the anatomical parts of the body which are involved in sexual reproduction and constitute Growth accelerates in the first half of puberty and stops at the completion of puberty. Human development is the process of Growing to maturity In biological terms this entails growth from a one-celled Zygote to an adult Human being Before puberty, body differences between boys and girls are almost entirely restricted to the genitalia. A sex organ, or primary sexual characteristic, as narrowly defined is any of the anatomical parts of the body which are involved in sexual reproduction and constitute During puberty, major differences of size, shape, composition, and function develop in many body structures and systems. The most obvious of these are referred to as secondary sex characteristics. Secondary sex characteristics are traits that distinguish the two Sexes of a species but that are not directly part of the Reproductive system.

In a strict sense, the term puberty (and this article) refers to the bodily changes of sexual maturation rather than the psychosocial and cultural aspects of adolescent development. An organism's sex is defined by the gametes it produces males produce male gametes (spermatozoa or Sperm) while females produce female gametes (ova or Egg cells; individual Adolescence is the period of psychological and social transition between childhood and adulthood. For the 2008 British film by Noel Clarke see Adulthood (film. Adolescence largely overlaps the period of puberty, but its boundaries are less precisely defined and it refers as much to the psychosocial and cultural characteristics of development during the teen years as to the physical changes of puberty.

Differences between male and female puberty

1 Follicle-stimulating hormone - FSH
2 Luteinizing hormone - LH
3 Progesterone
4 Estrogen
5 Hypothalamus
6 Pituitary gland
7 Ovary
8 Pregnancy - hCG (Human chorionic gonadotropin)
9 Testosterone
10 Testicle
11 Incentives
12 Prolactin - PRL

Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the major sex steroids involved. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors

Although there is a wide range of normal ages, on average, girls begin the process of puberty about 1-2 years earlier than boys (with average ages of nine to fourteen for girls and ten to seventeen for boys), and reach completion in a shorter time. ^[1] Girls attain adult height and reproductive maturity about 4 years after the first physical changes of puberty appear. In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.

The hormone that dominates female development is estradiol, an estrogen. Estradiol (17β-estradiol (also oestradiol) is a Sex hormone. Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, While estradiol promotes growth of breasts and uterus, it is also the principal hormone driving the pubertal growth spurt and epiphyseal maturation and closure. The uterus (from the Latin word for womb) is the major Female reproductive organ of most Mammals including Humans One end the Epiphysis is the name for a rounded end of a long Bone. The epiphysis is filled with red Bone marrow, which produces Erythrocytes, or red blood cells ^[2] Estradiol levels rise earlier and reach higher levels in women than in men.

In males, testosterone, an androgen, is the principal sex steroid. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine While testosterone produces all the male changes characterized as virilization, a substantial product of testosterone metabolism in males is estradiol, though levels rise later and more slowly than in girls. In biology and medicine virilization refers to the biological development of Sex differences, changes which make a Male body different from a Female body The male growth spurt also begins later, accelerates more slowly, and lasts longer before the epiphyses fuse. Although boys are 2 cm shorter than girls before puberty begins, adult men are on average about 13 cm (5. 2 inches) taller than women. Most of this sex difference in adult heights is attributable to a later onset of the growth spurt and a slower progression to completion,^[3] a direct result of the later rise and lower adult male levels of estradiol.

Puberty onset

Onset is associated with high GnRH pulsing, which precedes the rise in sex hormones, LH and FSH^[4]. Exogenous GnRH pulses cause the onset of puberty. ^[5] Brain tumors which increase GnRH output may also lead to premature puberty. ^[6]

The cause of this GnRH rise is contentious. Puberty begins consistently at around 47Kg for girls and 55Kg for boys. This dependence on bodyweight makes leptin a good candidate for causing GnRH rise. Leptin (Greek leptos meaning thin is a 16 kDa It is known that leptin has receptors in the hypothalamus^[7] which synthesises GnRH. Furthermore, individuals who are deficient in the leptin pathway fail to initiate puberty^[8]. The levels of leptin change in line with the onset of puberty, and then decline to adult levels.

Physical changes in males

Testicular size, function, and fertility

In boys, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche). Gonadarche refers to the earliest Gonadal changes of Puberty. ^[9] Testes in prepubertal boys change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cc in volume and about 1. The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male 5-2 cm in length. Testicular size continues to increase throughout puberty, reaching maximal adult size about 6 years later. ^[10] While 18-20 cc is reportedly an average adult size, there is wide variation in the normal population. ^[11]

The testes have two primary functions: to produce hormones and to produce sperm. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known The Leydig cells produce testosterone (as described below), which in turn produces most of the changes of male sexual maturation and maintains libido. Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the Seminiferous tubules in the testicle. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Libido in its common usage means Sexual desire however more technical definitions such as those found in the work of Carl Jung, are more general referring to libido However, most of the increasing bulk of testicular tissue is spermatogenic tissue (primarily Sertoli and interstitial cells). A Sertoli cell (a kind of Sustentacular cell) is a 'nurse' cell of the testes which is part of a Seminiferous tubule. The development of sperm production and fertility in males is not as well documented. Fertility is the natural capability of giving life As a measure "Fertility Rate" is the number of children born per couple person or population Sperm can be detected in the morning urine of most boys after the first year of pubertal changes (and occasionally earlier). Potential fertility is reached at about 13 years old in boys, but full fertility will not be gained until 14-16 years of age, although some go through the process faster, reaching it only 1 year later.

Pubic hair

Pubic hair often appears on a boy shortly after the genitalia begin to grow. Pubic hair is Hair in the frontal Genital area the crotch, and sometimes at the top of the inside of the legs these areas form the pubic region As in girls, the first appearance of pubic hair is termed pubarche and the pubic hairs are usually first visible at the dorsal (abdominal) base of the penis. The penis (plural penises, penes The first few hairs are described as stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too numerous to count. By stage 4, the pubic hairs densely fill the "pubic triangle. Pubic hair is Hair in the frontal Genital area the crotch, and sometimes at the top of the inside of the legs these areas form the pubic region " Stage 5 refers to spread of pubic hair to the thighs and upward towards the navel as part of the developing abdominal hair. In humans the thigh is the area between the Pelvis and the Knee. The navel (also called an umbilicus or colloquially belly button) is a Scar on the Abdomen, caused when the Umbilical cord is removed The term abdominal hair refers to the Hair that grows on the abdomen of humans and non-human Mammals, in the region between the Pubic area and

Body and facial hair

Facial hair of a male that has been shaved

In the months and years following the appearance of pubic hair, other areas of skin which respond to androgens develop heavier hair (androgenic hair) in roughly the following sequence: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the rest of the beard area. Facial hair is a Secondary sex characteristic in human Males Many Men start developing facial hair in the later years of Puberty, approximately Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. Androgenic hair, colloquially Body hair, is the Terminal hair on the Human body developed during and after Puberty. The axilla (or armpit, underarm, or oxter) is the area on the human body directly under the joint where the Arm connects to the Shoulder Androgenic hair, colloquially Body hair, is the Terminal hair on the Human body developed during and after Puberty. For the Swedish heavy metal band see Mustasch. A moustache (or mustache) is Facial hair grown on the upper Lip. Arm, leg, chest, abdominal, and back hair become heavier more gradually. The term chest hair is generally used to describe Hair that grows on the Chest of human males in the region between the Neck and the abdomen The term abdominal hair refers to the Hair that grows on the abdomen of humans and non-human Mammals, in the region between the Pubic area and There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different ethnic groups.

Voice change

Under the influence of androgens, the voice box, or larynx, grows in both genders. The larynx (plural larynges) colloquially known as the voicebox, is an organ in the Neck of Mammals involved in protection of the This growth is far more prominent in boys, causing the male voice to drop and deepen, sometimes abruptly but rarely "over night," about one octave, because the longer and thicker vocal folds have a lower fundamental frequency. In Music, an octave ( is the the use of which is "common in most musical systems The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of Mucous membrane stretched horizontally across the Larynx. The fundamental tone, often referred to simply as the fundamental and abbreviated fo, is the lowest frequency in a harmonic series. Voices never "break. " A typical 12-year old boy's larynx is larger, even before voice change, than an adult woman's. Occasionally, voice change is accompanied by unsteadiness of vocalization in the early stages of untrained voices. Most of the voice change happens during stage 3-4 of male puberty around the time of peak growth. Full adult pitch is attained at an average age of about 15 years. However, it usually precedes the development of significant facial hair by several months to years.

Gigantism: Precocious puberty

The name to a particular growth defect that occurs during childhood, from over-exposure to growth hormone. Gigantism or giantism, (from Greek gigas, gigantas " giant " is a condition characterized by excessive growth and height Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals Precocious puberty and a variety of conditions associated with excessive amounts of testosterone or estrogen in childhood will result in tallness by mid-childhood. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, People affected by Gigantism grow up in height up to 8ft (approximately 2. Gigantism or giantism, (from Greek gigas, gigantas " giant " is a condition characterized by excessive growth and height Height is the measurement of vertical Distance, but has two meanings in common use 40 metres) very rarely. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International However, the acceleration of bone maturation by the early rise of estradiol results in early completion of growth, and adult heights for these children may actually be below average for genetic potential. The possible symptoms is a Normal genetic variation or Hyperthyroidism, XYY syndrome, Overnutrition, Acromegaly, McCune-Albright syndrome etc. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine XYY syndrome is an Aneuploidy of the Sex chromosomes in which a Human Male receives an extra Y chromosome, producing a 47XYY Overnutrition is a form of Malnutrition in which nutrients are oversupplied relative to the amounts required for normal growth development and Metabolism. Acromegaly (from Greek akros "extreme" or "extremities" and megalos "large" - extremities enlargement is a Syndrome McCune-Albright syndrome ( polyostotic fibrous dysplasia) described in 1937 by Donovan James McCune and Fuller Albright, is a Genetic disorder

Male musculature and body shape

By the end of puberty, adult men have heavier bones and nearly twice as much skeletal muscle. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Some of the bone growth (e. g. , shoulder width and jaw) is disproportionately greater, resulting in noticeably different male and female skeletal shapes. The average adult male has about 150% of the lean body mass of an average female, and about 50% of the body fat.

This muscle develops mainly during the later stages of puberty, and muscle growth can continue even after a male is biologically adult. The peak of the so-called "strength spurt," the rate of muscle growth, is attained about one year after a male experiences his peak growth rate.

Body odor, skin changes, acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. As in girls, another androgen effect is increased secretion of oil (sebum) from the skin and the resultant variable amounts of acne. Acne can be prevented or diminished by antibacterial face washes and other compounds and typically fully diminishes at the end of puberty. Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive" are antimicrobial WASHING is one way of Cleaning, namely with Water and often some kind of Soap or Detergent.

Breast development: pubertal gynecomastia

Estradiol is produced from testosterone in male puberty as well as female, and male breasts often respond to the rising estradiol levels. Gynecomastia, or gynaecomastia, ˌgaɪnəkoʊˈmæstiə is the development of abnormally large Mammary glands in Males resulting in breast enlargement which Estradiol (17β-estradiol (also oestradiol) is a Sex hormone. The breast is the upper Ventral region of an animal’s Torso, particularly that of Mammals including Human beings. This is termed gynecomastia. In most boys, the breast development is minimal, similar to what would be termed a "breast bud" in a girl, but in some boys, breast growth is substantial. It usually occurs after puberty is underway, may increase for a year or two, and usually diminishes by the end of puberty. It is increased by extra adipose tissue if the boy is overweight. Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected Weight loss for overweight teenagers can help reduce the prominence of gynecomastia but not diminish as to pubertal reasons. Weight loss, in the context of Medicine or Health or Physical fitness, is a reduction of the total Body weight, due to a mean loss of fluid Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected

Although this is a normal part of male puberty for perhaps half of boys, breast development is usually as unwelcome as upper lip hair in girls, and can be removed surgically if it is causing a lot of stress or anxiety in the boy. Surgery (from the χειρουργική cheirourgikē, via chirurgiae meaning "hand work" is a medical specialty that uses operative manual and instrumental Anxiety is a physiological and psychological state characterized by Cognitive, Somatic, Emotional and Behavioral components

Physical changes in females

Breast development

Developing breasts in stage 4 of 5, with noticeable secondary mounds

The first physical sign of puberty in females is usually a firm, tender lump under the center of the areola(e) of one or both breasts, occurring on average at about 10. The breast is the upper Ventral region of an animal’s Torso, particularly that of Mammals including Human beings. This aritcle is about the breast tissue For the Entomology term see Glossary of Lepidopteran_terms#Wings. The breast is the upper Ventral region of an animal’s Torso, particularly that of Mammals including Human beings. 5 years of age. ^[12] This is referred to as thelarche. Thelarche is the first stage of secondary (postnatal Breast development usually occurring at the beginning of Puberty in girls By the widely used Tanner staging of puberty, this is stage 2 of breast development (stage 1 is a flat, prepubertal breast). The Tanner stages (also known as the Tanner scale) are stages of physical development in Children, Adolescents and Adults The stages Within six to 12 months, the swelling has clearly begun in both sides, softened, and can be felt and seen extending beyond the edges of the areolae. This is stage 3 of breast development. By another 12 months (stage 4), the breasts are approaching mature size and shape, with areolae and papillae forming a secondary mound. In its most general form a nipple is a Structure from which a fluid emanates In most young women, this mound disappears into the contour of the mature breast (stage 5), although there is so much variation in sizes and shapes of adult breasts that stages 4 and 5 are not always separately identifiable. ^[13]

Pubic hair

Pubic hair is often the second unequivocal change of puberty noticed, usually within a few months of thelarche. Pubic hair is Hair in the frontal Genital area the crotch, and sometimes at the top of the inside of the legs these areas form the pubic region ^[14] It is referred to as pubarche and the pubic hairs are usually visible first along the labia. Pubarche refers to the first appearance of Pubic hair in a child Labium (plural labia) is a Latin -derived term meaning " Lip " The first few hairs are described as Tanner stage 2. ^[13] Stage 3 is usually reached within another 6-12 months, when the hairs are too numerous to count and appear on the pubic mound as well. In Human anatomy or in mammals in general the mons pubis (Latin for " pubic mound " also known as the mons veneris (Latin mound of By stage 4, the pubic hairs densely fill the "pubic triangle. " Stage 5 refers to spread of pubic hair to the thighs and sometimes as abdominal hair upward towards the navel. In humans the thigh is the area between the Pelvis and the Knee. The term abdominal hair refers to the Hair that grows on the abdomen of humans and non-human Mammals, in the region between the Pubic area and The navel (also called an umbilicus or colloquially belly button) is a Scar on the Abdomen, caused when the Umbilical cord is removed In about 15% of girls, the earliest pubic hair appears before breast development begins. ^[14]

Vagina, uterus, ovaries

The mucosal surface of the vagina also changes in response to increasing levels of estrogen, becoming thicker and a duller pink in color (in contrast to the brighter red of the prepubertal vaginal mucosa). The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin covered in Epithelium, which are involved in The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, ^[15] Whitish secretions (physiologic leukorrhea) are a normal effect of estrogen as well. Leukorrhea (US or leukorrhoea (Commonwealth is a medical term that denotes a thick whitish Vaginal discharge ^[12] In the next 2 years following thelarche, the uterus and ovaries increase in size, and follicles in the ovaries reach larger sizes. The uterus (from the Latin word for womb) is the major Female reproductive organ of most Mammals including Humans One end the "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. Ovarian follicle is the basic unit of female reproductive biology and is composed of a roughly spherical aggregations of cells found in the Ovary. ^[16] The ovaries usually contain small follicular cysts visible by ultrasound. A cyst is a closed sac having a distinct membrane and Division on the nearby tissue. ^[17][18]

Menstruation and fertility

The first menstrual bleeding is referred to as menarche, and typically occurs about 2 years after thelarche. The menstrual cycle is a recurring cycle of physiologic changes that occurs in reproductive-age Females Overt menstruation (where there is blood flow from the Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings Thelarche is the first stage of secondary (postnatal Breast development usually occurring at the beginning of Puberty in girls ^[14] The average age of menarche in American girls is about 12. 75 years. ^[14] Menses (menstrual periods) are not always regular and monthly in the first 2 years after menarche. ^[19] Ovulation is necessary for fertility, but may or may not accompany the earliest menses. Note This article deals primarily with Human ovulation nonhuman Animal ovulation is touched on briefly at the conclusion Fertility is the natural capability of giving life As a measure "Fertility Rate" is the number of children born per couple person or population ^[20] In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year. ^[19] However, initiation of ovulation after menarche is not inevitable, and a high proportion of girls with continued irregularity several years from menarche will continue to have prolonged irregularity and anovulation, and are at higher risk for reduced fertility. ^[21] The word nubility is used commonly in the social sciences to designate achievement of fertility. Nubility is the state of being marriageable In a given Society, the level of nubility (those eligible for marriage compared to the level of Nuptiality (state of

Body shape, fat distribution, and body composition

During this period, also in response to rising levels of estrogen, the lower half of the pelvis and thus hips widen (providing a larger birth canal). The pelvis (pl pelvises or pelves) or pelvic girdle is the irregular bony structure located at the base of the spine (properly known The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus ^[13][22] Fat tissue increases to a greater percentage of the body composition than in males, especially in the typical female distribution of breasts, hips, buttocks, thighs, upper arms, and pubis. Progressive differences in fat distribution as well as sex differences in local skeletal growth contribute to the typical female body shape by the end of puberty. At age 10 years, the average girl has 6% more body fat than the average boy, but by the end of puberty the average difference is nearly 50%. ^[23]

Body odor, skin changes, and acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Body odor (spelled body odour outside the United States often abbreviated as B This often precedes thelarche and pubarche by 1 or more years. Another androgen effect is increased secretion of oil (sebum) from the skin. The sebaceous glands are Glands found in the Skin of Mammals Locations and morphology A branched type of Acinar gland, these This change increases the susceptibility to acne, a characteristic affliction of puberty greatly variable in its severity. Acne vulgaris (commonly called acne) is a Skin disease caused by changes in the Pilosebaceous units (skin structures consisting of a Hair follicle ^[24]

Variations

Typical puberty is described above, but many children vary with respect to timing of onset, tempo, steadiness of continuation, and sequence of events.

Timing of onset

Puberty is a process with a gradual onset beginning with changes of neuronal function in the hypothalamus, resulting in rising hormonal signals between brain and gonads, proceeding to gonadal growth and production of sex steroids, which in turn induce changes in responsive parts of the body. The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors The definition of onset, therefore, depends on the perspective (e. g. , hormonal versus physical) and purpose (establishing population normal standards, clinical care of early or late children, or a variety of other social purposes). The most commonly used definition of onset for both social and medical purposes is the appearance of the first physical changes described in this section of this article, but it should be understood that these physical changes are the first outward signs of preceding neural, hormonal, and gonadal function changes that are usually impossible or impractical to detect.

The age at which puberty begins can vary widely between individuals and between populations. Age of puberty is affected by both genetic factors and by environmental factors such as nutritional state or social circumstances. Timing may also be affected by environmental factors (exogenous hormones and environmental substances with hormone-like effects) and there is even evidence that life experiences may play a role as well.

Ethnic/racial differences have been recognized for centuries. For example, the average age of menarche in various populations surveyed in the last several decades has ranged from 12. Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings 0 to 18. 5 years. The earliest mean is reported for African-American girls and the oldest for high altitude subsistence populations in Asia. However, it is clear that much of the higher age averages reflect nutritional limitations more than genetic differences and can change within a few generations with a substantial change in diet. The median age of menarche for a population may be an index of the proportion of undernourished girls in the population, and the width of the spread may reflect unevenness of wealth and food distribution in a population.

Genetic influence

Various studies have found direct genetic effects to account for at least 46% of the variation of timing of puberty in well-nourished populations. ^{[25][26][27][28]} The genetic association of timing is strongest between mothers and daughters. The specific genes affecting timing are not defined yet. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance ^[25] Among the candidates is an androgen receptor gene. The androgen receptor ( AR) also known as NR3C4 (nuclear receptor subfamily 3 group C member 4 is a type of Nuclear receptor which is activated by ^[29]

Environmental factors

If genetic factors account for half of the variation of pubertal timing, environment factors are clearly important as well. One of the earliest observed environmental effects is that puberty occurs later in children raised at higher altitudes. The most important of the environmental influences is clearly nutrition, but a number of others have been identified, all which affect timing of female puberty and menarche more clearly than male puberty.

Nutritional influence

Nutritional factors are the strongest and most obvious environmental factors affecting timing of puberty. Nutrition (also called nourishment or aliment) is the provision to cells and Organisms of the materials necessary (in the form of food to support ^[25] Girls are especially sensitive to nutritional regulation because they must contribute all of the nutritional support to a growing fetus. Surplus calories (beyond growth and activity requirements) are reflected in the amount of body fat, which signals to the brain the availability of resources for initiation of puberty and fertility. This article is about the unit of energy For its use in Nutrition and Food labelling regulations, see the article on Food energy. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime "

Much evidence suggests that for most of the last few centuries, nutritional differences accounted for majority of variation of pubertal timing in different populations, and even among social classes in the same population. Recent worldwide increased consumption of animal protein, other changes in nutrition, and increases in childhood obesity have resulted in falling ages of puberty, mainly in those populations with the higher previous ages. In many populations the amount of variation attributable to nutrition is shrinking.

Although available dietary energy (simple calories) is the most important dietary influence on timing of puberty, quality of the diet plays a role as well. Lower protein intakes and higher plant fiber intakes, as occur with typical vegetarian diets, are associated with later onset and slower progression of female puberty. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Fiber crops are field crops grown for their Fibers which are used to make Paper, Cloth, or Rope. Vegetarianism is the practice of a diet that excludes Meat (including game and slaughter by-products Fish (including Shellfish and other sea

Studies have shown that calcium deficiency is a cause of late puberty, irregular and painful, cramping during menstruation with excessive blood loss, and lowered immune response to infections in young girls. This could be from a deficient diet or lack of vitamin D from too little sun exposure. This lack of calcium could predispose them to osteoporosis later in life.

Obesity influence

Scientific researchers have linked early obesity with a drop of puberty onset in girls. Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected They have cited obesity as a cause of breast development before nine years and menarche before twelve years. ^[30] Early puberty in girls can be a harbinger of later health problems. ^[31]

Physical activity and exercise

The average level of daily physical activity has also been shown to affect timing of puberty, especially female. A high level of exercise, whether for athletic or body image purposes, or for daily subsistence, reduces energy calories available for reproduction and slows puberty. The exercise effect is often amplified by a lower body fat mass.

Physical illness

Many chronic diseases can delay puberty in both boys and girls. Those that involve chronic inflammation or interfere with nutrition have the strongest effect. In the western world, inflammatory bowel disease and tuberculosis have been notorious for such an effect in the last century, while in areas of the underdeveloped world, chronic parasite infections are widespread. In Medicine, inflammatory bowel disease ( IBD) is a group of inflammatory conditions of the large intestine and Small intestine Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common Parasitism is a type of symbiotic relationship between Organisms of different Species. An infection is the detrimental Colonization of a host Organism by a foreign Species.

Environmental chemicals and hormones

There is theoretical concern, and animal evidence, that environmental hormones and chemicals may affect aspects of prenatal or postnatal sexual development in humans. A chemical substance is a Material with a definite chemical composition. Large amounts of incompletely metabolized estrogens and progestagens from pharmaceutical products are excreted into the sewage systems of large cities, and are sometimes detectable in the environment. Progestagens (also spelled progestogens or gestagens) are Hormones that produce effects similar to those of Progesterone, the only natural progestagen Sex steroids are sometimes used in cattle farming but have been banned in chicken meat production for 40 years. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors Although agricultural laws regulate use to minimize accidental human consumption, the rules are largely self-enforced in the United States. Significant exposure of a child to hormones or other substances that activate estrogen or androgen receptors could produce some or all of the changes of puberty. In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling

Harder to detect as an influence on puberty are the more diffusely distributed environmental chemicals like PCBs (polychlorinated biphenyl), which can bind and trigger estrogen receptors. Polychlorinated biphenyls ( PCB s are a class of Organic compounds with 1 to 10 Chlorine atoms attached to Biphenyl which is a molecule composed

More obvious degrees of partial puberty from direct exposure of young children to small but significant amounts of pharmaceutical sex steroids from exposure at home may be detected during medical evaluation for precocious puberty, but mild effects and the other potential exposures outlined above would not. Precocious puberty (La pubertas praecox) is an unusually early onset of Puberty, the process of sexual maturation triggered by the brain or exogenous chemicals which

Stress and social factors

Some of the least understood environmental influences on timing of puberty are social and psychological. In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years. Mechanisms of these social effects are unknown, though a variety of physiological processes, including pheromones, have been suggested based on animal research. A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural

The most important part of a child's psychosocial environment is the family, and most of the social influence research has investigated features of family structure and function in relation to earlier or later female puberty. Most of the studies have reported that menarche may occur a few months earlier in girls in high-stress households, whose fathers are absent during their early childhood, who have a stepfather in the home, who are subjected to prolonged sexual abuse in childhood, or who are adopted from a developing country at a young age. Sexual abuse, also referred to as molestation, is the forcing of undesired sexual acts by one person upon another International adoption, or intercountry adoption is a type of Adoption in which an individual or couple becomes the legal and permanent parents of a child born in another country Conversely, menarche may be slightly later when a girl grows up in a large family with a biological father present.

More extreme degrees of environmental stress, such as wartime refugee status with threat to physical survival, have been found to be associated with delay of maturation, an effect that may be compounded by dietary inadequacy.

Most of these reported social effects are small and our understanding is incomplete. Most of these "effects" are statistical associations revealed by epidemiologic surveys. Epidemiology is the study of factors affecting the Health and Illness of populations and serves as the foundation and Logic of interventions made in the Statistical associations are not necessarily causal, and a variety of covariables and alternative explanations can be imagined. Effects of such small size can never be confirmed or refuted for any individual child. Furthermore, interpretations of the data are politically controversial because of the ease with which this type of research can be used for political advocacy. Accusations of bias based on political agenda sometimes accompany scientific criticism.

Another limitation of the social research is that nearly all of it has concerned girls, partly because female puberty requires greater physiologic resources and partly because it involves a unique event (menarche) that makes survey research into female puberty much simpler than male. More detail is provided in the menarche article. Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings

Variations of tempo and progression

Tempo is the speed at which the process of pubertal changes progresses from beginning to end. The duration of puberty generally varies less than timing of onset, and approximates 4 years for girls and 6 for boys (from first physical changes to attainment of adult height). Nevertheless, some healthy children can proceed through puberty at a faster or slower tempo than most.

An interruption of progression of puberty is usually, but not always, due to abnormal causes such as malnutrition or anorexia nervosa. Malnutrition is a general term for a medical condition caused by an improper or insufficient diet. Anorexia Nervosa is a psychiatric Diagnosis that describes an Eating disorder characterized by low Body weight and Body image distortion Perhaps the most common apparently healthy variation is apparent interruption for a couple of years just after attainment of an early sign of initiation. For instance, some girls may seem to develop stage 2 breast buds at 6 or 7 years of age with no other signs of puberty, and nothing may happen for 2 or 3 years. Physicians refer to this as "unsustained puberty. "

Variations of sequence

The sequence of events of pubertal development can occasionally vary. For example, in about 15% of boys and girls, pubarche (the first pubic hairs) can precede, respectively, gonadarche and thelarche by a few months. Pubarche refers to the first appearance of Pubic hair in a child Gonadarche refers to the earliest Gonadal changes of Puberty. Thelarche is the first stage of secondary (postnatal Breast development usually occurring at the beginning of Puberty in girls Rarely, menarche can occur before other signs of puberty in a few girls. Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings These variations deserve medical evaluation because they can occasionally signal a disease.

Conclusion

In a general sense, the conclusion of puberty is reproductive maturity. Criteria for defining the conclusion may differ for different purposes: attainment of the ability to reproduce, achievement of maximal adult height, maximal gonadal size, or adult sex hormone levels. Maximal adult height is achieved at an average age of ~ 15 years for American girls and ~ 18 years for American boys. Potential fertility (sometimes termed nubility) usually precedes completion of growth by 1-2 years in girls and 3-4 years in boys. Stage 5 in the tables above typically represents maximal gonadal growth and attainment of adult hormone levels.

Neurohormonal process

The endocrine reproductive system consists of the hypothalamus, the pituitary, the gonads, and the adrenal glands, with input and regulation from many other body systems. Reproduction is the Biological process by which new individual Organisms are produced The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries. In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their True puberty is often termed "central puberty" because it begins as a process of the central nervous system. In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. A simple description of hormonal puberty is as follows:

1. The brain's hypothalamus begins to release pulses of GnRH. The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis Gonadotropin-releasing hormone ( GNRH) also known as Luteinizing-hormone releasing hormone ( LHRH) is a tropic Peptide Hormone
2. Cells in the anterior pituitary respond by secreting LH and FSH into the circulation. The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. Luteinizing hormone ( LH, also known as lutropin) is a Hormone produced by the Anterior pituitary gland. Follicle-stimulating hormone ( FSH) is a Hormone synthesized and secreted by Gonadotropes in the Anterior pituitary gland.
3. The ovaries or testes respond to the rising amounts of LH and FSH by growing and beginning to produce estradiol and testosterone. "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male Estradiol (17β-estradiol (also oestradiol) is a Sex hormone. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries
4. Rising levels of estradiol and testosterone produce the body changes of female and male puberty.

The onset of this neurohormonal process may precede the first visible body changes by 1-2 years.

Components of the endocrine reproductive system

The arcuate nucleus of the hypothalamus is the driver of the reproductive system. The arcuate nucleus (or infundibular nucleus is an aggregation of Neurons in the mediobasal Hypothalamus, adjacent to the Third ventricle and the Median The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis It has neurons which generate and release pulses of GnRH into the portal venous system of the pituitary gland. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The arcuate nucleus is affected and controlled by neuronal input from other areas of the brain and hormonal input from the gonads, adipose tissue and a variety of other systems. The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime "

The pituitary gland responds to the pulsed GnRH signals by releasing LH and FSH into the blood of the general circulation, also in a pulsatile pattern. The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea.

The gonads (testes and ovaries) respond to rising levels of LH and FSH by producing the steroid sex hormones, testosterone and estradiol. The testicle (from Latin testiculus, diminutive of testis, meaning "witness" virility plural testes) is the male "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. A steroid is a Terpenoid Lipid characterized by a Carbon skeleton with four fused rings generally arranged in a 6-6-6-5 fashion Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Estradiol (17β-estradiol (also oestradiol) is a Sex hormone.

The adrenal glands are a second source for steroid hormones. In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their Adrenal maturation, termed adrenarche, typically precedes gonadarche in mid-childhood. Adrenarche refers to a stage of maturation of the cortex of the human Adrenal glands It typically occurs between ages 6 and 10 years and involves both structural and functional

Major hormones

• GnRH (gonadotropin-releasing hormone) is a peptide hormone released from the hypothalamus which stimulates gonadotrope cells of the anterior pituitary. Gonadotropin-releasing hormone ( GNRH) also known as Luteinizing-hormone releasing hormone ( LHRH) is a tropic Peptide Hormone Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis Gonadotropes are basophilic cells in the Anterior pituitary which produce the Gonadotropins Follicle-stimulating hormone (FSH and The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea.
• LH (luteinizing hormone) is a larger protein hormone secreted into the general circulation by gonadotrope cells of the anterior pituitary gland. Luteinizing hormone ( LH, also known as lutropin) is a Hormone produced by the Anterior pituitary gland. The main target cells of LH are the Leydig cells of testes and the theca cells of the ovaries. Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the Seminiferous tubules in the testicle. The theca folliculi comprise a layer of the Ovarian follicles They appear as the follicles become Tertiary follicles The theca are divided into two layers the LH secretion changes more dramatically with the initiation of puberty than FSH, as LH levels increase about 25-fold with the onset of puberty, compared with the 2. 5-fold increase of FSH.
• FSH (follicle stimulating hormone) is another protein hormone secreted into the general circulation by the gonadotrope cells of the anterior pituitary. Follicle-stimulating hormone ( FSH) is a Hormone synthesized and secreted by Gonadotropes in the Anterior pituitary gland. The main target cells of FSH are the ovarian follicles and the Sertoli cells and spermatogenic tissue of the testes. Ovarian follicle is the basic unit of female reproductive biology and is composed of a roughly spherical aggregations of cells found in the Ovary. A Sertoli cell (a kind of Sustentacular cell) is a 'nurse' cell of the testes which is part of a Seminiferous tubule. Spermatogenesis is the process by which male Spermatogonia develop into mature Spermatozoa.
• Testosterone is a steroid hormone produced primarily by the Leydig cells of the testes, and in lesser amounts by the theca cells of the ovaries and the adrenal cortex. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries The theca folliculi comprise a layer of the Ovarian follicles They appear as the follicles become Tertiary follicles The theca are divided into two layers the Testosterone is the primary mammalian androgen and the "original" anabolic steroid. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine Anabolic steroids, or anabolic-androgenic steroids ( AAS) are a class of Steroid hormones related to the hormone Testosterone. It acts on androgen receptors in responsive tissue throughout the body. The androgen receptor ( AR) also known as NR3C4 (nuclear receptor subfamily 3 group C member 4 is a type of Nuclear receptor which is activated by
• Estradiol is a steroid hormone produced by aromatization of testosterone. Estradiol (17β-estradiol (also oestradiol) is a Sex hormone. A steroid is a Terpenoid Lipid characterized by a Carbon skeleton with four fused rings generally arranged in a 6-6-6-5 fashion Estradiol is the principal human estrogen and acts on estrogen receptors throughout the body. Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, The estrogen receptor (ER is a member of the nuclear hormone family of Intracellular receptors which is activated by the Hormone 17β-estradiol The largest amounts of estradiol are produced by the granulosa cells of the ovaries, but lesser amounts are derived from testicular and adrenal testosterone. A granulosa cell is a Somatic cell found closely associated with the developing female Gamete (called an Oocyte or egg
• Adrenal androgens are steroids produced by the zona reticulosa of the adrenal cortex in both sexes. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine The zona reticularis is the innermost layer of the Adrenal cortex, lying deep to the Zona fasciculata and superficial to the Adrenal medulla. Situated along the perimeter of the Adrenal gland, the adrenal cortex mediates the stress response through the production of Mineralocorticoids and Glucocorticoids The major adrenal androgens are dehydroepiandrosterone, androstenedione (which are precursors of testosterone), and dehydroepiandrosterone sulfate which is present in large amounts in the blood. Dehydroepiandrosterone ( DHEA) is a natural Steroid Prohormone produced from Cholesterol by the Adrenal glands the Gonads Androstenedione (also known as 4-androstenedione) is a 19- Carbon Steroid Hormone produced in the Adrenal glands and the Gonads Dehydroepiandrosterone ( DHEA) is a natural Steroid Prohormone produced from Cholesterol by the Adrenal glands the Gonads Adrenal androgens contribute to the androgenic events of early puberty in girls.
• IGF1 (insulin-like growth factor 1) rises substantially during puberty in response to rising levels of growth hormone and may be the principal mediator of the pubertal growth spurt. Insulin-like growth factor 1 (IGF-1 that was once called somatomedin C is a Polypeptide Protein Hormone similar in Molecular structure Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals
• Leptin is a protein hormone produced by adipose tissue. Leptin (Greek leptos meaning thin is a 16 kDa "Adipose" redirects here For the Doctor Who monster see " Partners in Crime " Its primary target organ is the hypothalamus. The leptin level seems to provide the brain a rough indicator of adipose mass for purposes of regulation of appetite and energy metabolism. Bioenergetics is the subject of a field of Biochemistry that concerns Energy flow through living systems It also plays a permissive role in female puberty, which usually will not proceed until an adequate body mass has been achieved.

Endocrine perspective

The endocrine reproductive system becomes functional by the end of the first trimester of fetal life. The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as Hormones The endocrine system is instrumental Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female The testes and ovaries become briefly inactive around the time of birth but resume hormonal activity until several months after birth, when incompletely understood mechanisms in the brain begin to suppress the activity of the arcuate nucleus. This has been referred to as maturation of the prepubertal "gonadostat," which becomes sensitive to negative feedback by sex steroids. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors

Gonadotropin and sex steroid levels fall to low levels (nearly undetectable by current clinical assays) for approximately another 8 to 10 years of childhood. Gonadotropins are Protein Hormones secreted by Gonadotrope cells of the Pituitary gland of Vertebrates Gonadotropin is sometimes A medical test is a kind of Medical procedure performed to detect, diagnose, or evaluate Disease, disease processes susceptibility and determine Evidence is accumulating that the reproductive system is not totally inactive during the childhood years. Subtle increases in gonadotropin pulses occur, and ovarian follicles surrounding germ cells (future eggs) double in number. Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed An ovum (plural ova) is a Haploid Female reproductive cell or Gamete.

Normal puberty is initiated in the hypothalamus, with de-inhibition of the pulse generator in the arcuate nucleus. This inhibition of the arcuate nucleus is an ongoing active suppression by other areas of the brain. The signal and mechanism releasing the arcuate nucleus from inhibition have been the subject of investigation for decades and remain incompletely understood. Leptin levels rise throughout childhood and play a part in allowing the arcuate nucleus to resume operation. Leptin (Greek leptos meaning thin is a 16 kDa If the childhood inhibition of the arcuate nucleus is interrupted prematurely by injury to the brain, it may resume pulsatile gonadotropin release and puberty will begin at an early age.

Neurons of the arcuate nucleus secrete gonadotropin releasing hormone (GnRH) into the blood of the pituitary portal system. These GnRH signals from the hypothalamus induce pulsed secretion of LH (and to a lesser degree, FSH) at roughly 1-2 hour intervals. In the years preceding physical puberty, these gonadotropin pulses occur primarily at night and are of very low amplitude, but as puberty approaches they can be detected during the day. By the end of puberty, there is little day-night difference in the amplitude and frequency of gonadotropin pulses.

An array of "autoamplification processes" increases the production of all of the pubertal hormones of the hypothalamus, pituitary, and gonads.

Regulation of adrenarche and its relationship to maturation of the hypothalamic-gonadal axis is not fully understood, and some evidence suggests it is a parallel but largely independent process coincident with or even preceding central puberty. Adrenarche refers to a stage of maturation of the cortex of the human Adrenal glands It typically occurs between ages 6 and 10 years and involves both structural and functional Rising levels of adrenal androgens (termed adrenarche) can usually be detected between 6 and 11 years of age, even before the increasing gonadotropin pulses of hypothalamic puberty. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine Adrenal androgens contribute to the development of pubic hair (pubarche), adult body odor, and other androgenic changes in both sexes. Pubarche refers to the first appearance of Pubic hair in a child Body odor (spelled body odour outside the United States often abbreviated as B The primary clinical significance of the distinction between adrenarche and gonadarche is that pubic hair and body odor changes by themselves do not prove that central puberty is underway for an individual child.

Hormonal changes in girls

As the amplitude of LH pulses increases, the theca cells of the ovaries begin to produce testosterone and smaller amounts of progesterone. Progesterone is a C-21 Steroid Hormone involved in the Female Menstrual cycle, Pregnancy (supports Gestation Much of the testosterone moves into nearby cells called granulosa cells. A granulosa cell is a Somatic cell found closely associated with the developing female Gamete (called an Oocyte or egg Smaller increases of FSH induce an increase in the aromatase activity of these granulosa cells, which converts most of the testosterone to estradiol for secretion into the circulation.

Rising levels of estradiol produce the characteristic estrogenic body changes of female puberty: growth spurt, acceleration of bone maturation and closure, breast growth, increased fat composition, growth of the uterus, increased thickness of the endometrium and the vaginal mucosa, and widening of the lower pelvis. The endometrium is the inner membrane of the Mammalian Uterus.

As the estradiol levels gradually rise and the other autoamplification processes occur, a point of maturation is reached when the feedback sensitivity of the hypothalamic "gonadostat" becomes positive. This attainment of positive feedback is the hallmark of female sexual maturity, as it allows the mid cycle LH surge necessary for ovulation. Note This article deals primarily with Human ovulation nonhuman Animal ovulation is touched on briefly at the conclusion

Levels of adrenal androgens and testosterone also increase during puberty, producing the typical androgenic changes of female puberty: pubic hair, other androgenic hair as outlined above, body odor, acne.

Growth hormone levels rise steadily throughout puberty. IGF1 levels rise and then decline as puberty ends. Insulin-like growth factor 1 (IGF-1 that was once called somatomedin C is a Polypeptide Protein Hormone similar in Molecular structure Growth finishes and adult height is attained as the estradiol levels complete closure of the epiphyses. Epiphysis is the name for a rounded end of a long Bone. The epiphysis is filled with red Bone marrow, which produces Erythrocytes, or red blood cells

Hormonal changes in boys

Early stages of male hypothalamic maturation seem to be very similar to the early stages of female puberty, though occurring about 1-2 years later.

LH stimulates the Leydig cells of the testes to make testosterone and blood levels begin to rise. For much of puberty, nighttime levels of testosterone are higher than daytime. Regularity of frequency and amplitude of gonadotropin pulses seems to be less necessary for progression of male than female puberty.

However, a significant portion of testosterone in adolescent boys is converted to estradiol. Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Estradiol mediates the growth spurt, bone maturation, and epiphyseal closure in boys just as in girls. Estradiol also induces at least modest development of breast tissue (gynecomastia) in a large proportion of boys. Gynecomastia, or gynaecomastia, ˌgaɪnəkoʊˈmæstiə is the development of abnormally large Mammary glands in Males resulting in breast enlargement which Boys who develop mild gynecomastia or even developing swellings under nipples during puberty are told the effects are temporary in some male teenagers due to high levels of Estradiol. Gynecomastia, or gynaecomastia, ˌgaɪnəkoʊˈmæstiə is the development of abnormally large Mammary glands in Males resulting in breast enlargement which In its most general form a nipple is a Structure from which a fluid emanates Estradiol (17β-estradiol (also oestradiol) is a Sex hormone.

Another hormonal change in males takes place during the teenage years for most young men. At this point in a males life the testosterone levels slowly rise, and most of the effects are mediated through the androgen receptors by way of conversion dehydrotestosterone in target organs (especially that of the bowels). Consequently, there is a transformation that takes place and the processes in which human waste and urine are released by the body are reversed.

Historical shift

The age at which puberty occurs has dropped significantly since the 1840s. Year 1840 ( MDCCCXL) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year ^[32][33][34] Researchers refer to this drop as the 'secular trend'. From 1840 through 1950, in each decade there was a drop of four months in the average age of menarche among Western European female samples. Year 1950 ( MCML) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar. In Norway, girls born in 1840 had their first menarche at average 17 years. Norway ( Norwegian: Norge ( Bokmål) or Noreg ( Nynorsk) officially the Kingdom of Norway, is a Constitutional In France in 1840 the average was 15. 3 years. In England the 1840 average was 16. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland 5 years for girls. In Japan the decline happened later and was then more rapid: from 1945 to 1975 in Japan there was a drop of 11 months per decade. For a topic outline on this subject see List of basic Japan topics.

See also

• Secondary sex characteristics
• Child sexuality
• Delayed puberty
• Menarche, gonadarche, pubarche, thelarche, adrenarche
• Precocious puberty

References

• Gordon, Catharine M. Secondary sex characteristics are traits that distinguish the two Sexes of a species but that are not directly part of the Reproductive system. Child sexuality refers to phenomena researched as the Sexual feelings behaviors and development of Children. Puberty is described as delayed when a boy or girl has passed the usual age of onset of Puberty with no physical or hormonal signs that it is beginning Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings Gonadarche refers to the earliest Gonadal changes of Puberty. Pubarche refers to the first appearance of Pubic hair in a child Thelarche is the first stage of secondary (postnatal Breast development usually occurring at the beginning of Puberty in girls Adrenarche refers to a stage of maturation of the cortex of the human Adrenal glands It typically occurs between ages 6 and 10 years and involves both structural and functional Precocious puberty (La pubertas praecox) is an unusually early onset of Puberty, the process of sexual maturation triggered by the brain or exogenous chemicals which ; Laufer, MR (2005). "Chapter 4: Physiology of puberty", in Emans SJH, Goldstein DP, Laufer, MR, eds. : Pediatric and Adolescent Gynecology, 5th ed. , Philadelphia: Lippincott, Williams & Wilkins, pp. 120–155. ISBN 0781744938.  
• Gungor, Neslihan; Arslanian SA (2002). "Chapter 21: Nutritional disorders: integration of energy metabolism and its disorders in childhood", in Sperling, MA ed. : Pediatric Endocrinology, 2nd ed. , Philadelphia: Saunders, pp. 689–724. ISBN 0721695396.  
• Marshall, William A. ; Tanner, JM (1986). "Chapter 8: Puberty", in Falkner F, Tanner JM, eds. : Human Growth: A Comprehensive Treatise, 2nd ed. , New York: Plenum Press, pp. 171–209. ISBN 0-306-41952-1.  
• Rosenfield, Robert L. (2002). "Chapter 16: Female puberty and its disorders", in Sperling, MA ed. : Pediatric Endocrinology, 2nd ed. , Philadelphia: Saunders, pp. 455–518. ISBN 0721695396.  
• Styne, Dennis M. (2002). "Chapter 18: The testes: disorders of sexual differentiation and puberty in the male", in Sperling, MA ed. : Pediatric Endocrinology, 2nd ed. , Philadelphia: Saunders, pp. 565–628. ISBN 0721695396.  

Further reading

• Ducros, A. and Pasquet, P. "Evolution de l'âge d'apparition des premières règles (ménarche) en France". Biométrie Humaine (1978), 13, 35–43.
• Herman-Giddens ME, Slora EJ, Wasserman RC, et al. "Secondary sexual characteristics and menses in young girls seen in office practice: a study from the pediatric research in office settings network". Pediatrics, 1997; 99:501-12. Newer data suggesting we should be using lower age thresholds for evaluation.
• Plant TM, Lee PA, eds. The Neurobiology of Puberty. Bristol: Society for Endocrinology, 1995. Proceedings of the latest (4th) International Conference on the Control of the Onset of Puberty, containing summaries of current theories of physiological control, as well as GnRH analog treatment.
• Tanner JM, Davies PS. "Clinical longitudinal standards for height and weight velocity for North American children". J Pediatr 1985; 107:317-29. Highly useful growth charts with integrated standards for stages of puberty.

External links

• Teen Forums - Puberty
• NIH guide to puberty and adolescence
• Growing Up Sexually: A World Atlas
• Pictures and detailed information about breast development during puberty
• Research shows how evolution explains age of puberty, ScienceDaily, December 1, 2005. Events 800 - Charlemagne judges the accusations against Pope Leo III in the Vatican Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar.
• Mark Hanson, P. Gluckman. Evolution, development and timing of puberty, Trends in Endocrinology & Metabolism, January 2006.
• Neurobiological Mechanisms of the Onset of Puberty in Primates, Endocrine Reviews, 2001 Feb;22(1):111-51.