甲状腺刺激ホルモン

解説

甲状腺刺激ホルモン，甲状腺の機能の発達、維持（甲状腺ホルモンの合成・放出）に関与する下垂体前葉ホルモンで、TSH（thyroid stimulating hormoneの略）と表記されることが多い。TSHは糖タンパクで、α(アルファ)とβ(ベータ)の2本の鎖からできている。分子量は2万5000～2万8000で、ホルモンとしての活性部位はβ鎖にある。正常なヒトの血漿(けっしょう)中ではTSHの濃度は1ミリリットル当り5ナノグラム以下で、分泌されたホルモンは代謝されて1時間たらずで半減してしまう。

作用

TSHは甲状腺濾胞細胞に存在する細胞膜を7回貫通するG蛋白質共役型受容体に結合して，濾胞細胞の増高，濾胞細胞のヨード摂取，サイログロブリンの生合成，コロイド滴の形成，甲状腺ホルモンの生合成および分泌の促進作用や甲状腺の重量増加作用を示す．

使用

Thyrogen (Genzyme).

定義

A hormone secreted by the anterior lobe of the pituitary gland. It increases the rate of removal of iodine from the blood by the thyroid gland, synthesis of the thyroid hormone, and its release into the bloodstream. The thyrotropic hormone is a protein with a low molecular weight (about 10,000) that contains some carbohydrate.

適応症

TSH, or thyrotropin, is a glycosylated protein of two subunits,  and . TSH stimulates the thyroid gland to produce thyroid hormones. Deficiencies are treated by giving thyroxine itself rather than TSH, but TSH is available for diagnostic purposes to differentiate between pituitary and thyroid gland failure as causes of hypothyroidism.

一般的な説明

The thyrotropic hormone, also called thyrotropin and thyroidstimulatinghormone (TSH), is a glycoprotein consisting oftwo polypeptide chains. This hormone promotes productionof thyroid hormones by affecting the kinetics of the mechanismby which the thyroid concentrates iodide ions from thebloodstream, thereby promoting incorporation of the halogeninto the thyroid hormones and release of hormones by thethyroid.
TSH (Thyropar) appears to be a glycoprotein (relativemolecular mass [Mr] 26,000–30,000) containing glucosamine,galactosamine, mannose, and fucose, whose homogeneityis yet to be established. It is produced by thebasophil cells of the anterior lobe of the pituitary gland.TSH enters the circulation from the pituitary, presumablytraversing cell membranes in the process. After exogenousadministration, it is widely distributed and disappears veryrapidly from circulation. Some evidence suggests that thethyroid may directly inactivate some of the TSH by an oxidationmechanism that may involve iodine. TSH thus inactivatedcan be reactivated by certain reducing agents.TSH regulates the production by the thyroid gland of thyroxine,which stimulates the metabolic rate. Thyroxinefeedback mechanisms regulate the production of TSH bythe pituitary gland.

臨床応用

Recombinant form of human thyroidstimulating hormone (rhTSH). Used diagnostically for serum thyroglobulin testing.