Adrenocorticotrophic hormone
ACTH belongs to the lipotrophin family of peptides which includes alpha-MSH and beta-endorphins. It is synthesised by corticotroph cells in the anterior and intermediate lobes of the pituitary from a large precursor molecule POMC - pro -opiomelanocortin.
Release of ACTH is controlled by:
- stimuli - corticotrophin-releasing factor, vasopressin, IL-1, catecholamines, physical or mental stress
- inhibitor - cortisol, by both a feedback loop to hypothalamus and pituitary
Patterns of ACTH secretion:
- 24 - hour rhythm - lowest levels during the early hours of sleep; peak levels just prior to waking
- episodes of secretion at meal times and every 1-3 hours
Effects of ACTH include:
- glucocorticoid production by the innermost layers of the adrenal cortex:
- increases cAMP within cells that:
- decreases cholesterol breakdown and increases cholesterol uptake from the blood
- activates the rate-limiting enzymes at the start of the steroid biosynthetic pathway
- cortisol production commences within minutes of an intravenous dose
- increases cAMP within cells that:
- minimal melanocyte stimulating hormone activity and has the ability to stimulate melanocytes if secreted in excess
- minimal release of aldosterone and sex steroids from adrenal cortex
Related pages
Create an account to add page annotations
Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.