A 35-year-old woman with severe endometriosis-related pain is started on a GnRH agonist (leuprolide acetate). Which of the following best describes the mechanism by which this drug reduces endometriotic lesions?

• A Direct cytotoxic effect on endometrial implants via receptor binding
• B Competitive antagonism at pituitary GnRH receptors causing immediate suppression
• C Aromatase inhibition within ectopic endometrial tissue
• D Initial flare followed by pituitary desensitization and hypoestrogenism ✓

Explanation

GnRH agonists initially stimulate gonadotropin release (flare effect) for 1 to 2 weeks, then cause downregulation of pituitary GnRH receptors through continuous stimulation, leading to profound hypoestrogenism. This hypoestrogenic state causes atrophy of endometriotic implants. GnRH antagonists, by contrast, cause immediate competitive blockade without the flare effect.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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