The pulsatile nature of GnRH release is critical for normal gonadotropin secretion. If GnRH is given as a continuous infusion rather than in pulses, which of the following changes occurs?

• A Sustained LH and FSH elevation due to constant gonadotroph stimulation
• B Selective suppression of FSH only because FSH is more sensitive to receptor desensitization
• C Downregulation of GnRH receptors causing paradoxical suppression of LH and FSH ✓
• D Paradoxical prolactin rise due to cross-reactivity at lactotroph GnRH receptors

Explanation

Continuous GnRH exposure causes homologous downregulation of GnRH receptors on gonadotrophs; the initial LH/FSH surge is followed by profound suppression — the basis for GnRH agonist use in prostate cancer and endometriosis. Pulsatile GnRH at physiologic 60–90 minute intervals is needed to maintain receptor number. Both LH and FSH are suppressed (not FSH selectively). Prolactin is not affected through this mechanism.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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