Ketoconazole was formerly used orally in Cushing syndrome before hepatotoxicity limited its use. Its endocrine action is best described as:
- A Inhibition of cytochrome P450-dependent enzymes of steroidogenesis, including CYP17A1 ✓
- B Competitive antagonist at the glucocorticoid receptor
- C Blockade of ACTH receptors on zona fasciculata cells
- D Irreversible inhibition of 5-alpha reductase
Correct answer: A. Inhibition of cytochrome P450-dependent enzymes of steroidogenesis, including CYP17A1
Explanation
Ketoconazole inhibits several cytochrome P450 steroidogenic enzymes, notably CYP17B1 (17-alpha-hydroxylase and 17,20-lyase) and also cholesterol side-chain cleavage, thereby reducing cortisol and androgen synthesis. This is a blockade of hormone production, not receptor antagonism, which distinguishes it from mifepristone at the glucocorticoid receptor.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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