Endocrine System MCAT Practice Question
A 54-year-old woman presents with a 6-month history of severe hot flashes occurring 8-10 times daily, night sweats that soak through her bedclothes, and irritable mood. Vital signs are normal. Laboratory studies show FSH 78 mIU/mL, LH 31 mIU/mL, and estradiol <5 pg/mL, consistent with menopause. She is started on transdermal estradiol 0.05 mg/day. Within 2 weeks, her hot flashes decrease by 80% and night sweats resolve, though her serum FSH and LH levels remain markedly elevated. Which of the following best explains the rapid improvement in vasomotor symptoms despite persistent elevation of gonadotropin levels?
Answer choices
- AEstrogen binds to receptors on neurons in the hypothalamus and brainstem that regulate thermoregulation and mood, directly modulating noradrenergic neurotransmission and stabilizing the core body temperature set pointCorrect answer
- BEstrogen stimulates the hypothalamic-pituitary axis to increase GnRH secretion, which rapidly normalizes the hypothalamic-pituitary-ovarian feedback loop
- CEstrogen replacement directly inhibits FSH and LH synthesis at the pituitary level, restoring negative feedback control and eliminating the hormonal drive for vasomotor symptoms
- DEstrogen increases bone resorption, releasing calcium stores that suppress parathyroid hormone and reduce sympathetic nervous system activation responsible for flushing
- EEstrogen acts as an antioxidant to reduce free radical-mediated damage to blood vessels, improving vascular reactivity and thermoregulation
- FEstrogen replacement restores ovarian steroidogenesis and local estrogen production within target tissues, bypassing the need for systemic gonadotropin signaling
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