Adrenocorticotropic Hormone (ACTH), Plasma Clinical Information
Discusses physiology, pathophysiology, and general clinical
aspects, as they relate to a laboratory test Adrenocorticotropic
hormone (ACTH), the primary stimulator of adrenal cortisol
production, is synthesized by the pituitary in response to
corticotropin-releasing hormone (CRH), which is released by the
hypothalamus. Plasma ACTH and cortisol levels exhibit peaks (6-8
a.m.) and nadirs (11 p.m.). Cortisol, the main glucocorticoid,
plays a central role in glucose metabolism and in the body's
response to stress. Only a small percentage of circulating
cortisol is biologically active (free form), with the majority
of cortisol inactive (protein bound). Cortisol is inactivated in
the liver and excreted in the urine as conjugated compounds
(largely 17-hydroxysteroids). Urine free cortisol levels reflect
circulating free plasma cortisol levels. Disorders of cortisol
production: - Cushing disease (pituitary ACTH-producing tumor) -
Ectopic ACTH-producing t