Adrenocorticotropic hormone (ACTH or corticotropin) is a polypeptide hormone synthesised from POMC, (pre-opiomelanocortin) and secreted from corticotropes in the anterior lobe of the pituitary gland in response to the hormone corticotropin-releasing hormone (CRH) released by the hypothalamus. It consists of 39 amino acids.
ACTH consists of 39 amino acids, the first 13 of which (counting from the N-terminus) may be cleaved to form ?-MSH. (This common structure is one reason that patients with hypercortisolism, in which ACTH levels are elevated, often present with excessively tanned skin.)
The half-life of ACTH in human blood is about 10 minutes.
ACTH acts through the stimulation of cell surface ACTH receptors, which are primarily located on the adrenocortical cells. ACTH stimulates the cortex of the adrenal gland and boosts the synthesis of corticosteroids, mainly glucocorticoids but also mineralcorticoids and sex steroids (androgens). Together with ACTH the hormones lipotropin, melanocyte-stimulating hormone (MSH), ?-endorphin and met-enkephalin are also released. ACTH is also related to the circadian rhythm in many organisms.
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