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{{Infobox_Disease |
 
{{Infobox_Disease |
 
Name = Hypothyroidism |
 
Name = Hypothyroidism |
Image = |
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Image = Triiodothyronine.svg |
Caption = |
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Caption = [[Triiodothyronine]], the most active form of [[thyroid hormone]] |
 
DiseasesDB = 6558 |
 
DiseasesDB = 6558 |
 
ICD10 = {{ICD10|E|03|9|e|00}} |
 
ICD10 = {{ICD10|E|03|9|e|00}} |
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MeshID = D007037 |
 
MeshID = D007037 |
 
}}
 
}}
'''Hypothyroidism''' is the disease state in humans and animals caused by insufficient production of [[thyroid hormone]] by the [[thyroid gland]]. There are several distinct causes for chronic hypothyroidism in human beings, the most common being [[Hashimoto's thyroiditis]] (an [[autoimmune]] disease) and [[radioiodine]] therapy for [[hyperthyroidism]]. Historically, [[iodine deficiency]] was the most common cause of hypothyroidism world-wide. The disease may also be caused by a lack of thyroid gland or a deficiency of hormones from either the hypothalamus or the pituitary.<br /><br />
+
'''Hypothyroidism''' is the disease state in humans and animals caused by insufficient production of [[thyroid hormone]] by the [[thyroid gland]].
   
'''Secondary hypothyroidism''' occurs if the [[pituitary gland]] does not create enough thyroid stimulating hormone (TSH) to induce the thyroid gland to create a sufficient quantity of [[thyroxine]]. Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused when the pituitary is damaged by a tumor, radiation, or surgery so that it is no longer able to instruct the thyroid to make enough hormone<ref name="ATA">ATA Hypothryoidism Booklet, pge 6, American Thyroid Association, 2003.</ref>. <br /><br />
+
==Causes==
  +
There are several distinct causes for chronic hypothyroidism. Historically, and still in many developing countries, [[iodine deficiency]] is the most common cause of hypothyroidism worldwide. In present day developed countries, however, 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.
   
'''Tertiary hypothyroidism''', also called '''hypothalamic-pituitary-axis hypothyroidism''', results when the hypothalamus fails to instruct the pituitary to produce sufficient TSH. <br /><br />
+
Hypothyroidism can result from postpartum [[thyroiditis]], a condition that affects about 5% of all women within a year after giving birth. The first phase is typically [[hyperthyroidism]]. 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. It is a relatively common disease in purebred domestic dogs as well, and can have a hereditary basis in [[dogs]].
+
Hypothyroidism can also result from sporadic inheritance, sometimes [[autosome|autosomal]] recessive.
   
It is claimed by some in the [[water fluoridation controversy]] that hypothyroidism is related to fluoride.
+
Hypothyroidism is also a relatively common hormone disease in domestic dogs, with some specific breeds having a definite predisposition.<ref>{{cite web |author=Brooks W |title=Hypothyroidism in Dogs |url=http://www.veterinarypartner.com/Content.plx?P=A&A=461 |work=The Pet Health Library |date=01/06/2008 |publisher=VetinaryPartner.com |accessdate=2008-02-28}}</ref>
   
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]].
+
Temporary hypothyroidism can be due to the [[Wolff-Chaikoff effect]].
   
==Signs and symptoms==
+
Hypothyroidism is often classified by the organ of origin:<ref>{{cite web |author=Simon H |title=Hypothyroidism |url=http://www.umm.edu/patiented/articles/what_causes_hypothyroidism_000038_2.htm |date=4/19/2006 |publisher=University of Maryland Medical Center |accessdate=2008-02-28}}</ref><ref>{{cite web |author=Department of Pathology |title=Pituitary Gland -- Diseases/Syndromes |url=http://www.pathology.vcu.edu/education/endocrine/endocrine/pituitary/diseases.html |date=June 13, 2005 |publisher=Virginia Commonwealth University (VCU) |accessdate=2008-02-28}}</ref>
Hypothyroidism has been called the "great imitator" for the vast number of medical conditions it can mimic:
 
   
:Thyroid hormones are essential and primary regulators of the body's [[metabolism]]. Imbalances can affect virtually every metabolic process in the body, exerting significant effects on mood and energy level. Thyroid function has a profound impact on overall health via its modulation of carbohydrate, protein, and fat metabolism, vitamin utilization, [[mitochondrial]] function, [[digestive]] process, muscle and nerve activity, blood flow, oxygen utilization, hormone secretion, sexual and reproductive health, and many other [[physiological]] parameters. <ref name="Geneva Diagnostics">Comprehensive Thyroid Assessment, [http://www.gdx.net/home/assessments/thyroid/ Geneva Diagnostics web site article]</ref>
+
{| class="wikitable"
  +
| '''Type''' || '''Origin''' || '''Description'''
  +
|-
  +
| ''Primary'' || [[thyroid gland]] || The most common forms include [[Hashimoto's thyroiditis]] (an [[autoimmune]] disease) and [[radioiodine]] therapy for [[hyperthyroidism]].
   
In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with:<ref name="Identifying hypothyroidism’s psychiatric presentations">Current Psychiatry Online, [http://www.currentpsychiatry.com/article_pages.asp?AID=4545&UID=29961]</ref>
+
|-
* atypical depression (which may present as dysthymia)
+
| ''Secondary'' || [[pituitary gland]] || Occurs if the pituitary gland does not create enough [[thyroid stimulating hormone]] (TSH) to induce the thyroid gland to create a sufficient quantity of [[thyroxine]]. Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused when the pituitary is damaged by a tumor, radiation, or surgery so that it is no longer able to instruct the thyroid to make enough hormone<ref name="ATA">{{cite book |author=American Thyroid Association (ATA) |title=Hypothyroidism Booklet |year=2003 |pages=6 |url=http://www.thyroid.org/patients/brochures/Hypothyroidism%20_web_booklet.pdf#search=%22hypothyroidism%22 |format=PDF}}</ref>
* bipolar spectrum syndrome (including manic-depression, mixed mania, bipolar depression, rapid-cycling bipolar disorder, cyclothymia, and premenstrual syndromes)
+
|-
* borderline personality disorder
+
| ''Tertiary'' || [[hypothalamus]] || Results when the hypothalamus fails to produce sufficient [[TRH]]. Hence may also be termed ''hypothalamic-pituitary-axis hypothyroidism''
* psychotic disorder (typically, paranoid psychosis)
+
|}
   
===Adults <ref>http://www.thyroid.org/patients/brochures/Hypothyroidism%20_web_booklet.pdf#search=%22hypothyroidism%22</ref>===
+
===General psychological associations===
  +
Hypothyroidism can be caused by [[Lithium pharmacology|lithium]]-based [[mood stabilizer]]s, usually used to treat [[bipolar disorder]] (previously known as manic depression).
  +
  +
In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with:<ref>{{cite journal |author=Heinrich TW, Grahm G |title=Hypothyroidism Presenting as Psychosis: Myxedema Madness Revisited |journal= |volume=5 |issue=6 |pages=260-266 |year=2003 |pmid=15213796 |doi=}}</ref><!-- this seems a broken link, or is subscription required:<ref name="Identifying hypothyroidism’s psychiatric presentations">Current Psychiatry Online, [http://www.currentpsychiatry.com/article_pages.asp?AID=4545&UID=29961]</ref> -->
  +
* atypical [[Clinical depression|depression]] (which may present as [[dysthymia]])
  +
* bipolar spectrum syndrome (including bipolar I or bipolar II disorder, [[cyclothymia]], or [[premenstrual syndrome]])
  +
* [[borderline personality disorder]]{{Fact|date=August 2007}}
  +
* a [[psychotic disorder]] (typically, paranoid [[schizophrenia]])
  +
* [[ADHD predominantly inattentive|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.
  +
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<ref name="Geneva Diagnostics">{{cite web |title=Comprehensive Thyroid Assessment |url=http://www.gdx.net/home/assessments/thyroid/ |publisher=Geneva Diagnostics |accessdate=2007-05-21}}</ref> to mention a few. 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:<ref name="ATA">{{cite book |author=American Thyroid Association (ATA) |title=Hypothyroidism Booklet |year=2003 |pages=6 |url=http://www.thyroid.org/patients/brochures/Hypothyroidism%20_web_booklet.pdf#search=%22hypothyroidism%22 |format=PDF}}</ref><ref name=nlm>{{MedlinePlus|000367|Hypothyroidism - primary}} - see list of Symptoms</ref>
  +
  +
====Early symptoms====
  +
* Poor muscle tone ([[muscle hypotonia]])
  +
* [[Fatigue (medical)|Fatigue]]
  +
* [[Cold intolerance]], increased sensitivity to cold
  +
* [[Constipation]]
  +
* [[Weight gain]]
  +
* [[Muscle cramps]] and [[joint pain]]
  +
* Thin, [[brittle fingernails]]
  +
* Thin, brittle hair
  +
* [[Paleness]]
  +
* Dry, itchy skin
  +
  +
====Late symptoms====
 
* Slowed speech and a [[hoarse]], breaking voice. Deepening of the voice can also be noticed.
 
* Slowed speech and a [[hoarse]], breaking voice. 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 [[memory]]
* Impaired cognitive function (brain fog)
+
* Impaired cognitive function ([[brain fog]]) and inattentiveness
 
* [[Urticaria]] (hives)
 
* [[Urticaria]] (hives)
 
* [[Migraine]] headache
 
* [[Migraine]] headache
* Increased sensitivity to heat and cold
 
 
* A [[bradycardia|slow heart rate]] with [[ECG]] changes including low voltage signals. Diminished cardiac output and decreased contractility.
 
* A [[bradycardia|slow heart rate]] with [[ECG]] changes including low voltage signals. Diminished cardiac output and decreased contractility.
  +
* [[Reactive hypoglycemia|Reactive (or post-prandial) hypoglycemia]]<ref name="pmid5086042">{{cite journal |author=Hofeldt FD, Dippe S, Forsham PH |title=Diagnosis and classification of reactive hypoglycemia based on hormonal changes in response to oral and intravenous glucose administration |journal=Am. J. Clin. Nutr. |volume=25 |issue=11 |pages=1193–201 |year=1972 |pmid=5086042 |doi= |url=http://www.ajcn.org/cgi/reprint/25/11/1193.pdf |format=PDF}}</ref>
 
* [[Pericardial effusion]]s may occur.
 
* [[Pericardial effusion]]s may occur.
 
* Sluggish [[reflex action|reflexes]]
 
* Sluggish [[reflex action|reflexes]]
* Dry puffy skin, especially on the face, and [[hair loss]], especially thinning of the outer third of the eyebrows
+
* [[hair loss]]
* [[clinical depression|Depression]] (especially in the elderly)
 
* Mild [[weight gain]]
 
 
* [[Anemia]] caused by impaired hemoglobin synthesis (decreased [[Erythropoietin|EPO]] levels), impaired intestinal iron and [[folate]] absorption or B12 deficiency from [[pernicious anemia]]
 
* [[Anemia]] caused by impaired hemoglobin synthesis (decreased [[Erythropoietin|EPO]] levels), impaired intestinal iron and [[folate]] absorption or B12 deficiency from [[pernicious anemia]]
* [[Slowed metabolism]]
 
* [[Constipation]]
 
* [[Fatigue (physical)]]
 
 
* [[anxiety]]/panic attacks
 
* [[anxiety]]/panic attacks
* [[Choking sensation]] or [[difficulty swallowing]]
+
* [[difficulty swallowing]]
 
* [[Shortness of breath]] with a shallow and slow respiratory pattern.
 
* [[Shortness of breath]] with a shallow and slow respiratory pattern.
 
* Impaired ventilatory responses to [[hypercapnia]] and [[Hypoxia (medical)|hypoxia]].
 
* Impaired ventilatory responses to [[hypercapnia]] and [[Hypoxia (medical)|hypoxia]].
 
* Increased need for sleep
 
* Increased need for sleep
* [[Muscle cramps]] and [[joint pain]]
 
* [[Brittle fingernails]]
 
 
* [[Osteopenia]] or [[Osteoporosis]]
 
* [[Osteopenia]] or [[Osteoporosis]]
* [[Paleness]]
+
* [[Irritability]] and mood instability
* [[Irritability]]
 
 
* Yellowing of the skin due to impaired conversion of [[beta-carotene]] to vitamin A
 
* Yellowing of the skin due to impaired conversion of [[beta-carotene]] to vitamin A
* Abnormal [[menstrual cycles]]
 
 
* Impaired renal function with decreased [[Glomerular filtration rate|GFR]].
 
* Impaired renal function with decreased [[Glomerular filtration rate|GFR]].
 
* Thin, fragile or absent [[eponychium|cuticles]]
 
* Thin, fragile or absent [[eponychium|cuticles]]
* [[Infertility]] or [[difficulty becoming pregnant]]
 
 
* [[Elevated serum cholesterol]]
 
* [[Elevated serum cholesterol]]
* [[Depression]]
 
* Mood instability
 
 
* Acute psychosis ([[myxedema madness]]) is a rare presentation of hypothyroidism
 
* Acute psychosis ([[myxedema madness]]) is a rare presentation of hypothyroidism
* Poor muscle tone ([[muscle hypotonia]])
+
* [[Decreased libido]]
* Decreased libido
+
* Decreased sense of taste and smell (late, less common symptoms)
  +
* Puffy face, hands and feet (late, less common symptoms)
  +
* Depression
   
Hypothyroidism in pediatric patients can cause the following additional symptoms:
+
===Pediatric===
* short stature
+
Hypothyroidism in [[Pediatrics|pediatric]] patients can cause the following additional symptoms:
* mental retardation
+
* [[short stature]]
  +
* [[mental retardation]] if present at birth, and untreated.
   
===Hypothyroidism in domestic dogs===
+
===Severity===
Hypothyroidism in dogs is a slowly progressive disease as well and can be difficult to diagnose accurately in the early stages. Dogs with hypothyroidism are plagued by a number of health problems including recurring skin infections and lethargic behavior. Hypothyroidism in dogs may also progress to myxedema coma.
+
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]].
It may also cause aggression in affected dogs. Dogs may show sudden weight gain, and hair loss at the base of the tail.
 
   
 
==Diagnostic testing==
 
==Diagnostic testing==
To diagnose primary hypothyroidism, many doctors simply measure the amount of [[Thyroid-stimulating hormone]] (TSH) being produced. 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 (fT3)). However, measuring just TSH fails to diagnose secondary and tertiary forms of hypothyroidism, thus leading to the following suggested minimum blood testing:
+
To diagnose primary hypothyroidism, many doctors simply measure the amount of [[Thyroid-stimulating hormone]] (TSH) being produced by the pituitary gland. 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 (fT3)). 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:
   
* thyroid-stimulating hormone (TSH)
 
 
* free triiodothyronine (fT3)
 
* free triiodothyronine (fT3)
 
* free levothyroxine (fT4)
 
* free levothyroxine (fT4)
 
* total T3
 
* total T3
 
* total T4
 
* total T4
  +
* 24 hour urine free T3 <ref name="24hurine">Baisier W. Hertoghe J. Eeckhaut W. Thyroid insufficiency. Is TSH the only diagnostic tool? J Nutr Environ ed. 2000;10:105-113. [http://www.ingentaconnect.com/content/routledg/cjne/2000/00000010/00000002/art00002"Thyroid insufficiency. Is TSH the only diagnostic tool?"]</ref>
   
 
Additionally, the following measurements may be needed:
 
Additionally, the following measurements may be needed:
* antithyroid antibodies - for evidence of [[autoimmune disease]]s that may be damaging the thyroid gland
+
* antithyroid [[antibodies]] - for evidence of [[autoimmune disease]]s that may be damaging the thyroid gland
 
* serum cholesterol - which may be elevated in hypothyroidism
 
* serum cholesterol - which may be elevated in hypothyroidism
 
* prolactin - as a widely available test of pituitary function
 
* prolactin - as a widely available test of pituitary function
  +
* testing for anemia, including ferritin
  +
  +
  +
'''Barnes Basal Temperature Test'''
  +
  +
The Barnes Basal Temperature Test was developed by the late Dr. Broda O. Barnes M.D. Ph.D. and first published in the Journal of the American Medical Association (JAMA) in August of 1942. This test involves placing a thermometer in the armpit for 10 minutes immediately upon waking, then taking the reading. (menstruating women must do the test on day 2-4 of their cycle)
  +
  +
According to Dr. Barnes, a reading below 36.6C (97.8F) is highly indicative of hypothyroidism, especially if accompanied by symptoms. The test was never widely adopted in the medical community, though a minority of doctors continue to employ it and attest to its effectiveness.
  +
<ref name="barnesfound">[http://brodabarnes.org"Broda O. Barnes MD, Research Foundation, Inc."]</ref>
  +
<ref name="unsuspect">[http://www.amazon.com/Hypothyroidism-Unsuspected-Illness-Broda-Barnes/dp/069001029X/ref=reader_auth_dp" Hypothyroidism: The Unsuspected Illness"]</ref>
   
 
==Treatment==
 
==Treatment==
{{main|Thyroid hormone#Medical use of thyroid hormones}}
+
{{main|Thyroid hormone#Medical use of thyroid hormones|l1=Medical use of thyroid hormones}}
A doctor can perform a blood test to see if a patient suffers from hypothyroidism. A synthetic thyroid supplement can be prescribed, which the patient must take daily to replace the missing hormone. The American Thyroid Association cautions against taking herbal remedies, and warns that taking too much iodine can actually worsen both hypothyroidism and hyperthyroidism. (See ATA Hypothyroidism Booklet, linked below.)
+
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 dosaging. The American Association of Clinical Endocrinologists recommends the use of [[levothyroxine]] (T4) as thyroid replacement. In general, desiccated thyroid hormone, combinations of thyroid hormone, or triiodothyronine should not be used for replacement therapy.<ref>{{cite journal |author=American Association of Clinical Endocrinologists |title=Medical Guidelines For Clinical Practice For The Evaluation And Treatment Of Hyperthyroidism And Hypothyroidism |journal=Endocrine Practice |volume=8 |issue=6 |year=2002 |month=November/Decemcer |pages=457-469 |url=http://www.aace.com/pub/pdf/guidelines/hypo_hyper.pdf |format=PDF}}</ref>
   
Patients with psychiatric symptoms (mood or psychosis) and physical symptoms of hypothyroidism, with [[subclinical hypothyroidism]] (normal TSH but low free T3) are often treated with thyroid supplement to bring the free T3 levels into the upper range of normal.
+
The American Thyroid Association cautions against taking herbal remedies, and warns that taking too much iodine can actually worsen hypothyroidism.<ref name="ATA"> </ref>
  +
  +
===Subclinical hypothyroidism===
  +
A [[meta-analysis]] by the [[Cochrane Collaboration]] found no benefit of thyroid hormone replacement except "some parameters of lipid profiles and left ventricular function".<ref name="pmid17636722">{{cite journal |author=Villar H, Saconato H, Valente O, Atallah A |title=Thyroid hormone replacement for subclinical hypothyroidism |journal=Cochrane database of systematic reviews (Online) |volume= |issue=3 |pages=CD003419 |year=2007 |pmid=17636722 |doi=10.1002/14651858.CD003419.pub2}}</ref>
  +
  +
==See also==
  +
*[[Goiters]]
  +
*[[Metabolism disorders]]
  +
*[[Thyrotropin]]
  +
*[[Thyroxine]]
  +
  +
==References==
  +
{{Reflist|2}}
   
 
== External links ==
 
== External links ==
*[http://www.thyroid.org/patients/brochures/Hypothyroidism%20_web_booklet.pdf#search=%22hypothyroidism%22 ATA Hypothyroidism Booklet]
+
*[http://brodabarnes.org Broda O. Barnes M.D., Research Foundation, Inc.]
*[http://www.thyroid.org/ American Thyroid Association]
+
*[http://www.hormone.org/public/thyroid.cfm Thyroid Section] of [[The Hormone Foundation]]
  +
*[http://www.endo-society.org The Endocrine Society]
 
*[http://www.aace.com/ American Association of Clinical Endocrinologists]
 
*[http://www.aace.com/ American Association of Clinical Endocrinologists]
 
*[http://thyroidfoundation.org/ American Foundation of Thyroid Patients]
 
*[http://thyroidfoundation.org/ American Foundation of Thyroid Patients]
 
*[http://www.allthyroid.org/ Thyroid Foundation of America]
 
*[http://www.allthyroid.org/ Thyroid Foundation of America]
+
*[http://www.thyroid.org.au/ Thyroid Australia]
==References==
+
*[http://www.mayoclinic.com/health/hypothyroidism/DS00353 Mayo Clinic: Hypothyroidism]
<references/>
 
*[http://www.veterinarypartner.com/Content.plx?P=A&A=461]
 
   
 
{{Endocrine pathology}}
 
{{Endocrine pathology}}
   
[[Category:Thyroid disease]]
+
[[Category:Thyroid disorders]]
  +
[[Category:Metabolism disorders]]
   
  +
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  +
[[pl:Niedoczynność tarczycy]]
 
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{{enWP|Hypothyroidism}}

Latest revision as of 20:08, March 24, 2008

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Triiodothyronine.svg|
Hypothyroidism
ICD-10 E039
ICD-9 244.9
OMIM [1]
DiseasesDB 6558
MedlinePlus [2]
eMedicine med/1145
MeSH {{{MeshNumber}}}

Hypothyroidism is the disease state in humans and animals caused by insufficient production of thyroid hormone by the thyroid gland.

CausesEdit

There are several distinct causes for chronic hypothyroidism. Historically, and still in many developing countries, iodine deficiency is the most common cause of hypothyroidism worldwide. In present day developed countries, however, 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.

Hypothyroidism can result from postpartum thyroiditis, a condition that affects about 5% of all women within a year after giving birth. The first phase is typically hyperthyroidism. 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.

Hypothyroidism is also a relatively common hormone disease in domestic dogs, with some specific breeds having a definite predisposition.[1]

Temporary hypothyroidism can be due to the Wolff-Chaikoff effect.

Hypothyroidism is often classified by the organ of origin:[2][3]

Type Origin Description
Primary thyroid gland The most common forms include Hashimoto's thyroiditis (an autoimmune disease) and radioiodine therapy for hyperthyroidism.
Secondary pituitary gland Occurs if the pituitary gland does not create enough thyroid stimulating hormone (TSH) to induce the thyroid gland to create a sufficient quantity of thyroxine. Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused when the pituitary is damaged by a tumor, radiation, or surgery so that it is no longer able to instruct the thyroid to make enough hormone[4]
Tertiary hypothalamus Results when the hypothalamus fails to produce sufficient TRH. Hence may also be termed hypothalamic-pituitary-axis hypothyroidism

General psychological associationsEdit

Hypothyroidism can be caused by lithium-based mood stabilizers, usually used to treat bipolar disorder (previously known as manic depression).

In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with:[5]

SymptomsEdit

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. 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[6] to mention a few. 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.

AdultsEdit

In adults, hypothyroidism is associated with the following symptoms:[4][7]

Early symptomsEdit

Late symptomsEdit

  • Slowed speech and a hoarse, breaking voice. 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 symptomsEdit

PediatricEdit

Hypothyroidism in pediatric patients can cause the following additional symptoms:

SeverityEdit

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.

Diagnostic testingEdit

To diagnose primary hypothyroidism, many doctors simply measure the amount of Thyroid-stimulating hormone (TSH) being produced by the pituitary gland. 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 (fT3)). 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
  • 24 hour urine free T3 [9]

Additionally, the following measurements may be needed:

  • 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


Barnes Basal Temperature Test

The Barnes Basal Temperature Test was developed by the late Dr. Broda O. Barnes M.D. Ph.D. and first published in the Journal of the American Medical Association (JAMA) in August of 1942. This test involves placing a thermometer in the armpit for 10 minutes immediately upon waking, then taking the reading. (menstruating women must do the test on day 2-4 of their cycle)

According to Dr. Barnes, a reading below 36.6C (97.8F) is highly indicative of hypothyroidism, especially if accompanied by symptoms. The test was never widely adopted in the medical community, though a minority of doctors continue to employ it and attest to its effectiveness. [10] [11]

TreatmentEdit

Main article: Thyroid hormone#Medical use of thyroid hormones

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 dosaging. The American Association of Clinical Endocrinologists recommends the use of levothyroxine (T4) as thyroid replacement. In general, desiccated thyroid hormone, combinations of thyroid hormone, or triiodothyronine should not be used for replacement therapy.[12]

The American Thyroid Association cautions against taking herbal remedies, and warns that taking too much iodine can actually worsen hypothyroidism.[4]

Subclinical hypothyroidismEdit

A meta-analysis by the Cochrane Collaboration found no benefit of thyroid hormone replacement except "some parameters of lipid profiles and left ventricular function".[13]

See alsoEdit

ReferencesEdit

  1. Brooks W. Hypothyroidism in Dogs. The Pet Health Library. VetinaryPartner.com. URL accessed on 2008-02-28.
  2. Simon H. Hypothyroidism. University of Maryland Medical Center. URL accessed on 2008-02-28.
  3. Department of Pathology. Pituitary Gland -- Diseases/Syndromes. Virginia Commonwealth University (VCU). URL accessed on 2008-02-28.
  4. 4.0 4.1 4.2 American Thyroid Association (ATA) (2003). Hypothyroidism Booklet (PDF), 6.
  5. Heinrich TW, Grahm G (2003). Hypothyroidism Presenting as Psychosis: Myxedema Madness Revisited 5 (6): 260-266.
  6. Comprehensive Thyroid Assessment. Geneva Diagnostics. URL accessed on 2007-05-21.
  7. MedlinePlus Encyclopedia 000367 - see list of Symptoms
  8. Hofeldt FD, Dippe S, Forsham PH (1972). Diagnosis and classification of reactive hypoglycemia based on hormonal changes in response to oral and intravenous glucose administration. Am. J. Clin. Nutr. 25 (11): 1193–201.
  9. Baisier W. Hertoghe J. Eeckhaut W. Thyroid insufficiency. Is TSH the only diagnostic tool? J Nutr Environ ed. 2000;10:105-113. "Thyroid insufficiency. Is TSH the only diagnostic tool?"
  10. "Broda O. Barnes MD, Research Foundation, Inc."
  11. " Hypothyroidism: The Unsuspected Illness"
  12. American Association of Clinical Endocrinologists (November/Decemcer 2002). Medical Guidelines For Clinical Practice For The Evaluation And Treatment Of Hyperthyroidism And Hypothyroidism. Endocrine Practice 8 (6): 457-469.
  13. Villar H, Saconato H, Valente O, Atallah A (2007). Thyroid hormone replacement for subclinical hypothyroidism. Cochrane database of systematic reviews (Online) (3): CD003419.

External links Edit


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