Hypothyroidism Classification and external resources
Thyroxine (T4) normally produced in 20:1 ratio to triiodothyronine (T3)
ICD-10	E03.9
ICD-9	244.9
DiseasesDB	6558
eMedicine	med/1145
MeSH	D007037

Hypothyroidism is the disease state in humans and animals caused by insufficient production of thyroid hormone by the thyroid gland. Thyroxine, or 353'5'-tetra­iodothyronine (often abbreviated as T4) a form of Thyroid hormones is the major Hormone secreted by the Triiodothyronine, C15[[hydrogen H12]] I3[[nitrogen N]] O4, also known as T3, is a Thyroid The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings E00-E35 - Endocrine diseases (E00-E07 Thyroid gland / Thyroid hormone ( Congenital iodine-deficiency syndrome ( The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. The Diseases Database is a free Website that provides information about the relationships between medical conditions Symptoms, and Medications. eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books The thyroid hormones, Thyroxine ( T4) and Triiodothyronine ( T3) are Tyrosine -based Hormones produced The thyroid is one of the largest Endocrine glands in the body Cretinism is a form of hypothyroidism found in infants. This article is about the medical term For the Marxist political concept see Parliamentary cretinism.

Contents 1 Causes 1.1 General psychological associations 2 Symptoms 2.1 Adults 2.1.1 Early symptoms 2.1.2 Late symptoms 2.1.3 Less common symptoms 2.2 Pediatric 2.3 Severity 3 Diagnostic testing 4 Treatment 4.1 Treatment Controversy 4.2 Subclinical hypothyroidism 5 References 6 External links

Causes

About three percent of the general population is hypothyroid. ^[1] Factors such as iodine deficiency or exposure to I-131 can increase that risk. There are a number of causes for overt hypothyroidism. Historically, and still in many developing countries, iodine deficiency is the most common cause of hypothyroidism worldwide. Iodine is an essential Trace element; the Thyroid hormones Thyroxine and Triiodotyronine contain iodine In iodine-replete individuals, hypothyroidism is mostly caused by Hashimoto's thyroiditis, or by a lack of the thyroid gland or a deficiency of hormones from either the hypothalamus or the pituitary. Hashimoto's thyroiditis or chronic lymphocytic thyroiditis is an Autoimmune disease where the body's own T-cells attack the cells of the Thyroid The thyroid is one of the largest Endocrine glands in the body

Hypothyroidism can result from postpartum thyroiditis, a condition that affects about 5% of all women within a year after giving birth. Thyroiditis is the inflammation of the thyroid gland The thyroid gland is located on the front of the neck below the Laryngeal prominence, and makes hormones that The first phase is typically hyperthyroidism. Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine Then, the thyroid either returns to normal or a woman develops hypothyroidism. Of those women who experience hypothyroidism associated with postpartum thyroiditis, one in five will develop permanent hypothyroidism requiring life-long treatment.

Hypothyroidism can also result from sporadic inheritance, sometimes autosomal recessive. An autosome is a non-sex Chromosome. It is an ordinarily paired type of chromosome that is the same in both Sexes of a species.

Hypothyroidism is also a relatively common hormone disease in domestic dogs, with some specific breeds having a definite predisposition. ^[2]

Temporary hypothyroidism can be due to the Wolff-Chaikoff effect. A very high intake of iodine can be used to temporarily treat hyperthyroidism, especially in an emergency situation. Although iodine is substrate for thyroid hormones, high levels prompt the thyroid gland to take in less of the iodine that is eaten, reducing hormone production.

Hypothyroidism is often classified by the organ of origin:^[3][4]

Type	Origin	Description
Primary	thyroid gland	The most common forms include Hashimoto's thyroiditis (an autoimmune disease) and radioiodine therapy for hyperthyroidism. The thyroid is one of the largest Endocrine glands in the body Hashimoto's thyroiditis or chronic lymphocytic thyroiditis is an Autoimmune disease where the body's own T-cells attack the cells of the Thyroid Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues Iodine-131 (131I, also called radioiodine, is a Radioisotope of Iodine which has medical and pharmaceutical uses Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine
Secondary	pituitary gland	Occurs if the pituitary gland does not create enough thyroid stimulating hormone (TSH) to induce the thyroid gland to produce enough thyroxine and triiodothyronine. The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused by damage to the pituitary gland, as by a tumor, radiation, or surgery. [5]
Tertiary	hypothalamus	Results when the hypothalamus fails to produce sufficient thyrotropin-releasing hormone (TRH). The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis TRH prompts the pituitary gland to produce thyrotropin (TSH). Hence may also be termed hypothalamic-pituitary-axis hypothyroidism.

General psychological associations

Hypothyroidism can be caused by lithium-based mood stabilizers, usually used to treat bipolar disorder (previously known as manic depression). Lithium in pharmacology refers to use of the Lithium Ion, Li+ as a drug This article refers to the medication For other uses see Stabilizer.

In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with:^[6]

• atypical depression (which may present as dysthymia)
• bipolar spectrum syndrome (including bipolar I or bipolar II disorder, cyclothymia, or premenstrual syndrome)
• borderline personality disorder
• a psychotic disorder (typically, paranoid schizophrenia)
• inattentive ADHD or sluggish cognitive tempo

Symptoms

The ability of hypothyroidism to mimic a number of medical conditions originates in the vast functions of the thyroid hormones, which are reduced or absent in this case. Major depressive disorder, also known as major depression, unipolar depression, unipolar disorder, clinical depression, or simply depression Dysthymia (pronounced /dɪsˈθaɪmiə/ is a Mood disorder that falls within the depression spectrum. Cyclothymia (pronounced /ˌsaɪkləˈθaɪmiə ˌsɪklə-/ is a Mood disorder. Premenstrual syndrome ( PMS) (sometimes referred to as PMT or Premenstrual Tension) is a collection of physical psychological and emotional symptoms Borderline personality disorder ( BPD) is a psychiatric diagnosis in the Diagnostic and Statistical Manual of Mental Disorders ( DSM-IV Personality Psychosis (from the Greek ψυχή "psyche" for mind or soul and -οσις "-osis" for abnormal condition with adjective psychotic Schizophrenia ( from the Greek roots schizein (σχίζειν "to split" and phrēn ADHD predominantly inattentive (ADHD-I is one of the three subtypes of Attention-deficit hyperactivity disorder (ADHD Sluggish Cognitive Tempo (SCT is an unformalized descriptive term which is used to better identify what appears to be a homogeneous sub-subgroup within the formal subgroup ADHD predominantly The functions of thyroid hormones include modulation of carbohydrate, protein and fat metabolism, vitamin utilization, mitochondrial function, digestive process, muscle and nerve activity, blood flow, oxygen utilization, hormone secretion and sexual and reproductive health^[7] to mention a few. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Thus, when the thyroid hormone content gets out of balance, systems covering the whole body are affected. This is why hypothyroidism can look like other diseases. Conversely, sometimes other conditions can be mistaken for hypothyroidism.

Adults

In adults, hypothyroidism is associated with the following symptoms:^[5][8]

Early symptoms

• Poor muscle tone (muscle hypotonia)
• Fatigue
• Cold intolerance, increased sensitivity to cold
• Depression
• Constipation
• Muscle cramps and joint pain
• Arthritis
• Goiter
• Thin, brittle fingernails
• Thin, brittle hair
• Paleness
• Dry, itchy skin
• Weight gain
• Bradycardia (low HR <60 BPM)

Late symptoms

• Slowed speech and a hoarse, breaking voice. Hypotonia is a condition of abnormally low Muscle tone (the amount of tension or resistance to movement in a muscle often involving reduced muscle strength Cold sensitivity or cold intolerance is unusual discomfort felt by some people when in a cool environment In the fields of Psychology and Psychiatry, the terms depression or depressed refer to both expected and pathologically chronic or severe Constipation, costiveness, or irregularity, is a condition of the Digestive system in which a person (or animal experiences hard Feces that Cramps, sometimes called Charley horses are unpleasant often painful sensations caused by contraction or over shortening of Muscles Cramps can be caused by cold Arthralgia (from Greek arthro-, joint + -algos, pain literally means joint pain; it is a symptom of injury infection illnesses -- in particular Arthritis (from Greek arthro-, joint + -itis, inflammation plural arthritides is a group of conditions involving damage to the Joints of the body A goitre ( BrE) or goiter ( AmE) ( Latin struma) also called a bronchocele, is a swelling in the neck (just below the Brittle nails is a condition where the nails are fragile and break frequently Pallor (also called pastiness or wanness) is a reduced amount of oxy Hemoglobin in Skin or Mucous membrane, a pale color which can Weight gain is an increase in Body weight. This can be either an increase in Muscle mass, fat deposits or excess fluids such as Water. Deepening of the voice can also be noticed.
• Dry puffy skin, especially on the face
• Thinning of the outer third of the eyebrows
• Abnormal menstrual cycles
• Low basal body temperature

Less common symptoms

• Heat intolerance, increased sensitivity to heat
• Impaired memory
• Impaired cognitive function (brain fog) and inattentiveness
• Urticaria (hives)
• Migraine headache
• A slow heart rate with ECG changes including low voltage signals. 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 Basal body temperature is the body temperature measured immediately after awakening and before any physical activity has been undertaken In Psychology, memory is an organism's ability to store retain and subsequently retrieve information Compare Brain fag Brain fog or mental clouding is a general sensation of unusually poor mental function associated with Migraine is a neurological Syndrome characterized by altered bodily experiences painful headaches and nausea Bradycardia, as applied to adult medicine is defined as a resting Heart rate of under 60 beats per minute though it is seldom symptomatic until the rate drops below 50 beat/min Diminished cardiac output and decreased contractility.
• Reactive (or post-prandial) hypoglycemia^[9]
• Pericardial effusions may occur. Reactive hypoglycemia is a medical term describing recurrent episodes of symptomatic Hypoglycemia occurring 2-4 hours after a high Carbohydrate meal (or oral Pericardial effusion ("fluid around the heart" is an abnormal accumulation of fluid in the Pericardial cavity.
• Sluggish reflexes
• Hair loss
• Anemia caused by impaired hemoglobin synthesis (decreased EPO levels), impaired intestinal iron and folate absorption or B12 deficiency from pernicious anemia
• Anxiety/panic attacks
• Difficulty swallowing
• Shortness of breath with a shallow and slow respiratory pattern. A reflex action, also known as a reflex, is an involuntary and almost instant movement in response to stimulus. Baldness involves the state of lacking hair where it often grows especially on the head Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative Erythropoietin (ɨˌɹɪθɹoʊˈpɔɪɨtɨn /ɨˌɹɪθɹoʊˈpɔɪtən/ or /ɨˌɹiːθɹoʊ-/ or EPO is a Glycoprotein Hormone that controls Folic acid (also known as Vitamin M and Folacin) and Folate (the Anionic form are forms of the water-soluble Vitamin B9 Pernicious anemia (also known as Biermer's anemia, Addison's anemia, or Addison-Biermer anemia) is a form of Megaloblastic anemia due to Anxiety is a physiological and psychological state characterized by Cognitive, Somatic, Emotional and Behavioral components Dysphagia should not be confused with the similarly pronounced Dysphasia, a language disorder Dyspnea or dyspnoea (pronounced disp-nee-ah, IPA /dɪsp'niə/ from Latin dyspnoea, from Greek dyspnoia from
• Impaired ventilatory responses to hypercapnia and hypoxia. Hypercapnia or hypercapnea (from the Greek hyper = "above" and kapnos = " Smoke " also known as hypercarbia is Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate
• Increased need for sleep
• Osteopenia or Osteoporosis
• Irritability and mood instability
• Yellowing of the skin due to impaired conversion of beta-carotene to vitamin A
• Impaired renal function with decreased GFR. Osteopenia is a condition where Bone mineral density is lower than normal Osteoporosis is a Disease of Bone that leads to an increased risk of fracture. Irritability is an excessive response to stimuli. Irritability takes many forms from the Contraction of a Unicellular organism when touched to complex Beta-carotene is an Organic compound - a Terpenoid, a red-orange pigment abundant in plants and fruits Renal function, in Nephrology, is an indication of the state of the Kidney and its role in Renal physiology.
• Thin, fragile or absent cuticles
• Elevated serum cholesterol
• Acute psychosis (myxedema madness) is a rare presentation of hypothyroidism
• Decreased libido
• Decreased sense of taste and smell (late, less common symptoms)
• Puffy face, hands and feet (late, less common symptoms)
• Depression

Pediatric

Hypothyroidism in pediatric patients was previously classified as Cretinism, and can cause the following symptoms:

• short stature
• mental retardation if present at birth, and untreated. The eponychium or cuticle in Human anatomy refers to the thickened layer of Skin surrounding fingernails and toenails. Hypercholesterolemia (literally high blood cholesterol is the presence of high levels of Cholesterol in the blood. Myxedema psychosis, more colloquially known as myxedema madness, is a relatively uncommon consequence of Hypothyroidism, particularly Hashimoto's thyroiditis 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 Pediatrics (also spelled paediatrics) is the branch of Medicine that deals with the medical care of Infants Children and Adolescents This article is about the medical term For the Marxist political concept see Parliamentary cretinism. Short stature refers to a height of a human being which is below expected Mental retardation is a generalized triarchic disorder characterized by subaverage cognitive functioning and deficits in two or more adaptive behaviors with onset before the age

Severity

The severity of hypothyroidism varies widely. Some have few overt symptoms, others with moderate symptoms can be mistaken for having other diseases and states. Advanced hypothyroidism may cause severe complications including cardiovasular and psychiatric myxedema. Myxedema (British English myxoedema) is a skin and tissue disorder usually due to severe prolonged Hypothyroidism.

Diagnostic testing

To diagnose primary hypothyroidism, many doctors simply measure the amount of Thyroid-stimulating hormone (TSH) being produced by the pituitary gland. Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the High levels of TSH indicate that the thyroid is not producing sufficient levels of Thyroid hormone (mainly as thyroxine (T₄) and smaller amounts of triiodothyronine (T₃)). The thyroid hormones, Thyroxine ( T4) and Triiodothyronine ( T3) are Tyrosine -based Hormones produced Thyroxine, or 353'5'-tetra­iodothyronine (often abbreviated as T4) a form of Thyroid hormones is the major Hormone secreted by the However, measuring just TSH fails to diagnose secondary and tertiary forms of hypothyroidism, thus leading to the following suggested blood testing if the TSH is normal and hypothyroidism is still suspected:

• free triiodothyronine (fT₃)
• free levothyroxine (fT₄)
• total T₃
• total T₄

Additionally, the following measurements may be needed:

• 24 hour urine free T₃ ^[10]
• antithyroid antibodies - for evidence of autoimmune diseases that may be damaging the thyroid gland
• serum cholesterol - which may be elevated in hypothyroidism
• prolactin - as a widely available test of pituitary function
• testing for anemia, including ferritin

Treatment

Main article: Medical use of thyroid hormones

Hypothyroidism is treated with the levorotatory forms of thyroxine (L-T₄) and triiodothyronine (L-T₃). Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Autoimmune diseases arise from an overactive Immune response of the body against substances and tissues normally present in the body The thyroid hormones, Thyroxine ( T4) and Triiodothyronine ( T3) are Tyrosine -based Hormones produced Both synthetic and animal-derived thyroid tablets are available and can be prescribed for patients in need of additional thyroid hormone. Thyroid hormone is taken daily, and doctors can monitor blood levels to help assure proper dosing. There are several different treatment protocols in thyroid replacement therapy:

T₄ Only

This treatment protocol involves supplementation of levothyroxine alone, in a synthetic form. It is currently the standard treatment in mainstream medicine. ^[11]

T₄ and T₃ in Combination

This treatment protocol involves administering both synthetic L-T₄ and L-T₃ simultaneously in combination. ^[12]

Desiccated Thyroid Extract

Desiccated thyroid extract is an animal based thyroid extract, most commonly from a porcine source. Desiccated thyroid or thyroid extract, refers to porcine (or mixed beef and pork Thyroid glands dried and powdered for therapeutic use It is also a combination therapy, containing natural forms of L-T₄ and L-T₃. ^[13]

Treatment Controversy

Though the current standard treatment in thyroid therapy is levothyroxine only, there exists some controversy about which treatment protocol is most effective. Some publications have challenged the status quo, stating that combination therapies can be more effective. ^[12][13] The American Association of Clinical Endocrinologists (AACE) states that desiccated thyroid hormone, combinations of thyroid hormone, or triiodothyronine should not generally be used for replacement therapy. ^[11]

Some studies have shown no improvement in mood or mental abilities for those on combination therapy, and possibly impaired well-being from subclinical hyperthyroidism. ^[14] T3 when used on its own as a treatment results in wide fluctuations across the course of a day in the thyroid hormone levels, and with combined T3/T4 therapy there continues to be wide variation throughout each day. ^[15] A 2007 metaanalysis of the nine controlled studies so far published found no significant difference in the effect on psychiatric symptoms. ^[16]

Subclinical hypothyroidism

Subclinical hypothyroidism occurs when thyrotropin (TSH) levels are elevated but thyroxine (T₄) and triiodothyronine (T₃) levels are normal. ^[17] In primary hypothyroidism, TSH levels are high and T₄ and T₃ levels are low. Endocrinologists are puzzled because TSH usually increases when T₄ and T₃ levels drop. TSH prompts the thyroid gland to make more hormone. Endocrinologists are unsure how subclinical hypothyroidism affects cellular metabolic rates (and ultimately the body's organs) because the levels of the active hormones are adequate. Some have proposed treating subclinical hypothyroidism with levothyroxine, the typical treatment for overt hypothyroidism, but the benefits and the risks are unclear. Reference ranges have been debated as well. The American Association of Clinical Endocrinologists (ACEE) supports a narrower TSH range, especially when the person has clinical signs of thyroid disease. This reference range may reduce the risks of goiter, thyroid nodules, thyroid cancer, and overt hypothyroidism, but remains controversial. ^[18] There is always the risk of overtreatment and hyperthyroidism. Some studies have suggested that subclinical hypothyroidism does not need to be treated. A meta-analysis by the Cochrane Collaboration found no benefit of thyroid hormone replacement except "some parameters of lipid profiles and left ventricular function". In Statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses The Cochrane Collaboration is a group of over 11500 volunteers in more than 90 countries who apply a rigorous systematic process to review the effects of interventions tested in biomedical ^[19]

References

External links

• Thyroid Section of The Hormone Foundation
• Thyroid Science journal
• The Endocrine Society
• American Association of Clinical Endocrinologists
• American Foundation of Thyroid Patients
• Thyroid Foundation of America
• Thyroid Australia
• Mayo Clinic: Hypothyroidism
• AHSTA: Hypothyroidism in Thyroid Autoimmunity

The Hormone Foundation, established in 1997 by The Endocrine Society as its public education affiliate serves as a resource for physicians patients and the public by

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic