A 16-year-old girl with idiopathic precocious puberty is treated with a GnRH agonist. The therapeutic benefit in this condition depends on which pharmacological phenomenon?
- A Competitive antagonism at gonadotropin receptors
- B Direct inhibition of estrogen synthesis in the ovaries
- C Paradoxical downregulation and desensitization of pituitary GnRH receptors ✓
- D Enhanced negative feedback at the hypothalamic level
Correct answer: C. Paradoxical downregulation and desensitization of pituitary GnRH receptors
Explanation
Continuous administration of GnRH agonists causes receptor downregulation and desensitization of gonadotrophs, paradoxically suppressing FSH and LH secretion. This reduces gonadal sex steroid production, halting precocious puberty. The same mechanism is exploited in endometriosis, uterine fibroids, and prostate cancer where sex hormone suppression is desired.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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