Further delineation of hypothalamic dysfunction responsible for menopausal hot flashes.

An association exists between pulsatile LH release and hot flashes (HFs). To further delineate the hypothalamic mechanism(s) responsible for HF, the basal levels and pulsatile release of LH, FSH, estradiol, and estrone and the rate of occurrence of HFs (measured objectively) were evaluated in patients with a defect of GnRH secretion [isolated gonadotropin deficiency (IGD)], patients with abnormalities of afferent input to GnRH neurons [hypothalamic amenorrhea (HA)], and postmenopausal women with severe HFs. Patients with IGD had received estrogens, which were discontinued before study. Patients with HA had experienced regular menses before disease onset, which followed emotional stress or weight loss. Studies were limited to HA patients with estrogen levels in the postmenopausal range. Pulsatile LH release was absent in patients with IGD and was absent or greatly reduced in women with HA. Objectively measured and subjectively experienced HFs occurred in IGD but not in HA patients. These results suggest that HFs are not an obligatory consequence of low endogenous estrogen levels and that the absence of episodic LH and GnRH release (IGD) does not influence the occurrence of HFs. It is possible that the dysfunction of afferent input to GnRH neurons in HA somehow prevents HFs in these women with low endogenous estrogen secretion.