A 28-year-old woman with infertility due to chronic anovulation is started on clomiphene citrate. The mechanism by which it promotes ovulation is:
- A Direct stimulation of ovarian granulosa cells
- B Agonism of dopamine receptors in the anterior pituitary
- C Antagonism of estrogen receptors in the hypothalamus ✓
- D Inhibition of aromatase in peripheral adipose tissue
Correct answer: C. Antagonism of estrogen receptors in the hypothalamus
Explanation
Clomiphene is a selective estrogen receptor modulator that blocks estrogen receptors in the hypothalamus, reducing negative feedback and increasing GnRH pulse frequency. This raises FSH and LH secretion, which stimulates follicular development and ovulation. Direct ovarian stimulation is not its mechanism. Dopamine agonism is used for prolactinomas. Aromatase inhibition is the mechanism of letrozole, another ovulation induction agent.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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