Mechanism of action
The peptide hormone in the anterior pituitary that influences glucocorticoid biosynthesis is ACTH
(corticotropin), whereas the peptide hormone in the hypothalamus is corticotropin-releasing factor (CRF). The
production of both ACTH and CRF is regulated by the central nervous system and by a negative corticoid
feedback mechanism. The CRF is released by the hypothalamus and is transported to the anterior pituitary,
where it stimulates the release of ACTH into the bloodstream. Then, ACTH is transported to the adrenal glands,
where it stimulates the biosynthesis and secretion of the glucocorticoids. The circulating levels of
glucocorticoids act on the hypothalamus and anterior pituitary to regulate the release of both CRF and ACTH.
As the levels of glucocorticoids rise, smaller amounts of CRF and ACTH are secreted, and a negative feedback
is observed (HPA suppression). Stimuli, such as pain, noise, and emotional reactions, increase the secretion of
CRF, ACTH, and consequently, the glucocorticoids. Once the stimulus is alleviated or removed, the negative
feedback mechanism inhibits further production and helps to return the body to a normal hormonal balance
(15,16).
