Pulsatile GnRH secretion from the hypothalamus is essential for normal gonadotropin secretion. In a patient treated with a continuous (non-pulsatile) GnRH agonist for prostate cancer, the long-term effect on LH and FSH secretion is:

• A Initial spike followed by paradoxical suppression of LH and FSH due to receptor downregulation ✓
• B Sustained increase in LH and FSH leading to hyper-stimulation
• C Selective suppression of FSH with preserved LH
• D No change because pituitary gonadotrophs adapt by upregulating GnRH receptors

Explanation

Continuous GnRH agonist administration causes an initial flare (transient rise in LH and FSH), followed by desensitization and downregulation of GnRH receptors on pituitary gonadotrophs, resulting in profound suppression of LH, FSH, and subsequently testosterone. This medical castration effect is exploited therapeutically in prostate cancer and endometriosis. Pulsatile GnRH (every 60–90 minutes) is required for physiological gonadotropin stimulation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.