Thyroid-stimulating hormone
330361
226109935
2008-07-16T21:28:32Z
Boghog2
2428506
[[WP:UNDO|Undid]] revision 226103556 by [[Special:Contributions/118.94.91.129|118.94.91.129]] ([[User talk:118.94.91.129|talk]]): What are the bad effects of increased TSH? Perhaps hypothyroidism?
{{protein
| Name = [[Chorionic gonadotropin alpha|Thyroid-stimulating hormone, alpha]] (Glycoprotein hormones, alpha polypeptide)
| caption =
| image =
| width =
| HGNCid = 1885
| Symbol = [[Chorionic gonadotropin alpha|CGA]]
| AltSymbols = HCG, GPHa, GPHA1
| EntrezGene = 1081
| OMIM = 118850
| RefSeq = NM_000735
| UniProt = P01215
| PDB =
| ECnumber =
| Chromosome = 6
| Arm = q
| Band = 14
| LocusSupplementaryData = -q21
}}
{{Protein
|Name=Thyroid-stimulating hormone, beta
|image=
|caption=
|Symbol=TSHB
|AltSymbols=
|HGNCid=12372
|Chromosome=1
|Arm=p
|Band=13
|LocusSupplementaryData=
|ECnumber=
|OMIM=188540
|EntrezGene=7252
|RefSeq=NM_000549
|UniProt=P01222
|PDB=
}}
'''Thyroid-stimulating hormone''' (also known as '''TSH''' or '''thyrotropin''') is a [[peptide hormone]] synthesized and secreted by [[thyrotrope]] cells in the [[anterior pituitary gland]] which regulates the endocrine function of the [[thyroid gland]].<ref name="Sacher">{{cite book |last= Sacher|first= Ronald|coauthors= Richard A. McPherson|title= Wildmann's Clinical Interpretation of Laboratory Tests, 11th ed.|year= 2000|publisher= F.A. Davis Company|isbn= 0-8036-0270-7}}</ref>
==Physiology==
===Controlling the rate of release===
TSH stimulates the thyroid gland to secrete the hormones [[thyroxine]] (T<sub>4</sub>) and [[triiodothyronine]] (T<sub>3</sub>).<ref>{{GeorgiaPhysiology|5/5ch5/s5ch5_4}}</ref> TSH production is controlled by a Thyrotrophin Releasing Hormone, ([[TRH]]), which is manufactured in the [[hypothalamus]] and transported to the [[anterior pituitary gland]] via the [[superior hypophyseal artery]], where it increases TSH production and release. [[Somatostatin]] is also produced by the hypothalamus, and has an opposite effect on the pituitary production of TSH, decreasing or inhibiting its release.
The level of thyroid hormones (T<sub>3</sub> and T<sub>4</sub>) in the blood have an additional effect on the pituitary release of TSH; When the levels of T<sub>3</sub> and T<sub>4</sub> are low, the production of TSH is increased, and conversely, when levels of T<sub>3</sub> and T<sub>4</sub> are high, then TSH production is decreased. This effect creates a regulatory negative [[feedback loop]].
===Subunits of TSH===
TSH is a glycoprotein and consists of two subunits, the ''alpha'' and the ''beta'' subunit.
* The [[Alpha subunit of glycoprotein hormones|α (''alpha'') subunit]] (i.e., [[chorionic gonadotropin alpha]]) is identical to that of [[human chorionic gonadotropin]] (HCG), [[luteinizing hormone]] (LH), [[follicle-stimulating hormone]] (FSH).
* The β (''beta'') subunit is unique to TSH, and therefore determines its function.
===The TSH receptor===
The [[TSH receptor]] is found mainly on thyroid [[follicular cells]]<ref>Parmentier M, Libert F, Maenhaut C, Lefort A, Gérard C, Perret J, Van Sande J, Dumont JE and Vassart G., Molecular cloning of the thyrotropin receptor, Science 246 (1989), 1620-1622</ref>. Stimulation of the receptor increases T<sub>3</sub> and T<sub>4</sub> production and secretion.
Stimulating antibodies to this receptor mimic TSH action and are found in [[Graves-Basedow disease|Graves' disease]].
==Diagnostic use==
TSH levels are tested in the blood of patients suspected of suffering from excess ([[hyperthyroidism]]), or deficiency ([[hypothyroidism]]) of thyroid hormone. Generally, a normal range for TSH for adults is between 0.4 and 5.0 [[Micro-|u]][[international unit|IU]]/mL (equivalent to [[milli|m]]IU/L), but values vary slightly among labs. The optimal goal TSH level for patients on treatment ranges between 0.3 to 3.0 mIU/L.<ref>[http://www.aace.com/newsroom/press/2006/index.php?r=20060110 American Association of Clinical Endocrinologists<!-- Bot generated title -->]</ref>. The interpretation depends also on what the blood levels of thyroid hormones (T<sub>3</sub> and T<sub>4</sub>) are. The [[National Health Service]] in the UK considers a "normal" range to be more like 0.1 to 5.0 uIU/mL.{{Fact|date=April 2007}}
TSH levels for children normally start out much higher. In [[2002]], the [[National Academy of Clinical Biochemistry]] (NACB) in the [[United States]] recommended age-related reference limits starting from about 1.3-19 uIU/mL for normal term infants at birth, dropping to 0.6-10 uIU/mL at 10 weeks old, 0.4-7.0 uIU/mL at 14 months and gradually dropping during childhood and puberty to adult levels, 0.4-4.0 uIU/mL.<ref>{{cite web| last =Demers| first =Laurence M.| authorlink =| coauthors =Carole A. Spencer| title = LMPG: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease| work =| publisher =[[National Academy of Clinical Biochemistry]] (USA)| date =2002| url =http://www.nacb.org/lmpg/thyroid_LMPG_PDF.stm |format =| doi =| accessdate =2007-04-13 }} - see ''Section 2. Pre-analytic factors''</ref>
The NACB also stated that it expected the normal (95%) range for adults to be reduced to 0.4-2.5 uIU/mL, because research had shown that adults with an initially measured TSH level of over 2.0 uIU/mL had "an increased odds ratio of developing [[hypothyroidism]] over the [following] 20 years, especially if thyroid antibodies were elevated".<ref>{{cite web| last =Demers| first =Laurence M.| authorlink =| coauthors =Carole A. Spencer| title = LMPG: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease| work =| publisher =[[National Academy of Clinical Biochemistry]] (USA)| date =2002| url =http://www.nacb.org/lmpg/thyroid_LMPG_PDF.stm |format =| doi =| accessdate =2007-04-13 }} - see ''Section 3.C.Thyrotropin/ Thyroid Stimulating Hormone (TSH) measurement</ref>
{| class="wikitable"
| '''Source of pathology''' || '''TSH level''' || '''thyroid hormone level''' || '''Disease causing conditions'''
|-
| hypothalamus/pituitary || high || high || benign [[tumor of the pituitary]] ([[adenoma]]) or [[thyroid hormone resistance]]
|-
| hypothalamus/pituitary || low || low || [[hypopituitarism]]
|-
| thyroid || low || high || [[hyperthyroidism]] or [[Grave's disease]]
|-
| thyroid || high || low || [[congenital hypothyroidism]] (cretinism), [[hypothyroidism]]
|}
Clearly, both TSH and T<sub>3</sub> and T<sub>4</sub> should be measured to ascertain where a specific thyroid dysfunction is caused by primary pituitary or by a primary thyroid disease. If both are up (or down) then the problem is probably in the pituitary. If the one component (TSH) is up, and the other (T<sub>3</sub> and T<sub>4</sub>) is down, then the disease is probably in the thyroid itself. The same holds for a low TSH, high T3 and T4 finding.
A TSH assay is now also the recommended screening tool for thyroid disease. Recent advances in increasing the sensitivity of the TSH assay make it a better screening tool than free T<sub>4</sub>.<ref name="Sacher">{{{{cite book |last= Sacher|first= Ronald|coauthors= Richard A. McPherson|title= Wildmann's Clinical Interpretation of Laboratory Tests, 11th ed.|year= 2000|publisher= F.A. Davis Company|isbn= 0-8036-0270-7}}</ref>
==Therapeutic use==
A drug, recombinant human TSH (rhTSH), called Thyrogen, is manufactured by [[Genzyme|Genzyme Corp.]] in Cambridge, Massachusetts. The rhTSH is used in patients with thyroid cancer which is related to tumoral factors.
==Footnotes==
<references/>
==External links==
* {{MedlinePlus|003684}}
* {{MeshName|Thyrotropin}}
{{Hormones}}
[[Category:Glycoproteins]]
[[Category:Peptide hormones]]
[[Category:Anterior pituitary hormones]]
[[Category:HPT axis]]
[[bs:Tireostimulišući hormon]]
[[cs:Thyreotropní hormon]]
[[da:TSH]]
[[de:Thyreotropin]]
[[dv:ތައިރޮއިޑް ސްޓިމިއުލޭޓިންގ ހޯރމޯން]]
[[es:Tirotropina]]
[[fr:Thyréostimuline]]
[[id:Hormon Tirotrop]]
[[it:Ormone tireostimolante]]
[[he:תירוטרופין]]
[[lt:Tireotropinas]]
[[hu:Thyreoidea-stimuláló hormon]]
[[mk:Тиреотропин]]
[[nl:Thyroïdstimulerend hormoon]]
[[ja:甲状腺刺激ホルモン]]
[[no:Tyroideastimulerende hormon]]
[[pl:Hormon tyreotropowy]]
[[pt:Hormônio estimulante da tiróide]]
[[ru:Тиреотропный гормон]]
[[sk:Tyreotropín]]
[[sr:Тиреостимулишући хормон]]
[[fi:Tyreotropiini]]
[[sv:Tyreoideastimulerande hormon]]