A 58-year-old man on spironolactone for heart failure develops tender gynecomastia after six months. The mechanism of spironolactone-induced gynecomastia involves:

• A Increased aromatase activity converting testosterone to estradiol
• B Direct stimulation of breast tissue estrogen receptors
• C Prolactin hypersecretion from the anterior pituitary
• D Blockade of androgen receptors and inhibition of testosterone biosynthesis ✓

Explanation

Spironolactone has structural similarity to steroid hormones and acts as an antiandrogen by blocking androgen receptors and inhibiting 17-alpha-hydroxylase, reducing testosterone biosynthesis. This hormonal imbalance causes gynecomastia. Eplerenone, a more selective mineralocorticoid receptor antagonist, lacks these antiandrogen effects and is preferred when gynecomastia develops. Spironolactone does not increase aromatase activity or prolactin secretion.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.