|
Adrenocorticotropic hormone (ACTH), also known as corticotropin (INN, BAN) (brand names Acortan, ACTH, Acthar, Acton, Cortigel, Trofocortina), is a polypeptide tropic hormone produced and secreted by the anterior pituitary gland. It is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress (along with its precursor corticotropin-releasing hormone from the hypothalamus). Its principal effects are increased production and release of cortisol by the cortex of the adrenal gland. Primary adrenal insufficiency, also called Addison's disease, occurs when adrenal gland production of cortisol is chronically deficient, resulting in chronically elevated ACTH levels; when a pituitary tumor is the cause of elevated ACTH (from the anterior pituitary) this is known as Cushing's disease and the constellation of signs and symptoms of the excess cortisol (hypercortisolism) is known as Cushing's syndrome. Conversely, deficiency of ACTH is a cause of secondary adrenal insufficiency, often as a result of hypopituitarism. ACTH is also related to the circadian rhythm in many organisms. In addition to its endogenous role, ACTH is used clinically as a diagnostic agent in assessing adrenal function.〔〔〔 == Production and regulation == POMC, ACTH and β-lipotropin are secreted from corticotropes in the anterior lobe (or adenohypophysis) of the pituitary gland in response to the hormone corticotropin-releasing hormone (CRH) released by the hypothalamus. ACTH is synthesized from pre-pro-opiomelanocortin (pre-POMC). The removal of the signal peptide during translation produces the 241-amino acid polypeptide POMC, which undergoes a series of post-translational modifications such as phosphorylation and glycosylation before it is proteolytically cleaved by endopeptidases to yield various polypeptide fragments with varying physiological activity. These fragments include:〔(【引用サイトリンク】url=http://www.uniprot.org/uniprot/P01189 )〕 In order to regulate the secretion of ACTH, many substances secreted within this axis exhibit slow/intermediate and fast feedback-loop activity. Glucocorticoids secreted from the adrenal cortex work to inhibit CRH secretion by the hypothalamus, which in turn decreases anterior pituitary secretion of ACTH. Glucocorticoids may also inhibit the rates of POMC gene transcription and peptide synthesis. The latter is an example of a slow feedback loop, which works on the order of hours to days, whereas the former works on the order of minutes. The half-life of ACTH in human blood is about ten minutes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Adrenocorticotropic hormone」の詳細全文を読む スポンサード リンク
|