What response is expected after administration of metyrapone in normal individuals?

Metyrapone is a medication that inhibits the enzyme 11-beta-hydroxylase, which is involved in cortisol synthesis in the adrenal glands. When metyrapone is administered to normal individuals, cortisol levels decrease because the drug impedes its production. In response to the drop in cortisol, the hypothalamus detects the low cortisol levels and stimulates the pituitary gland to increase the secretion of adrenocorticotropic hormone (ACTH).

This feedback mechanism is part of the hypothalamic-pituitary-adrenal (HPA) axis. Since normal individuals have an intact feedback loop, the expected physiological response to a decrease in cortisol is an increase in ACTH output due to reduced negative feedback inhibition. Therefore, increased ACTH output is the correct response expected after administering metyrapone in normal individuals, reflecting the body's attempt to compensate for the reduced cortisol production.

In normal circumstances, this is a key aspect of adrenal function and hormonal regulation, showcasing the intricate balance and response of the endocrine system to changes in hormone levels.