A 28-year-old woman presents with amenorrhea and galactorrhea. MRI reveals a 4 mm pituitary microadenoma. Which of the following best explains why elevated prolactin causes amenorrhea?
- A Prolactin directly inhibits ovarian estrogen synthesis
- B Prolactin suppresses hypothalamic GnRH pulsatility, reducing LH and FSH secretion ✓
- C Prolactin stimulates somatostatin release, which inhibits FSH
- D Prolactin competes with LH at ovarian receptors
Correct answer: B. Prolactin suppresses hypothalamic GnRH pulsatility, reducing LH and FSH secretion
Explanation
Hyperprolactinemia suppresses the hypothalamic pulse generator responsible for GnRH secretion, reducing pulsatile LH and FSH release and thereby causing hypogonadotropic hypogonadism. Prolactin does not directly act on ovarian steroidogenesis nor does it compete with LH at receptors. The mechanism is entirely at the hypothalamic level via enhanced dopaminergic tone and direct inhibition of GnRH neurons.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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