Estrogen raises the sweating threshold in postmenopausal women with hot flashes.

OBJECTIVE To determine if estrogen ameliorates hot flashes by raising the core body temperature sweating threshold, by reducing core body temperature fluctuations, and/or by reducing sympathetic activation (as measured by plasma 3-methoxy-4-hydroxyphenylglycol). DESIGN Laboratory physiological study. SETTING University medical center. PATIENT(S) Twenty-four healthy postmenopausal women reporting frequent hot flashes. INTERVENTION(S) Participants were randomly assigned, in double-blind fashion, to receive 1 mg/d 17beta-estradiol orally or placebo for 90 days. MAIN OUTCOME MEASURE(S) Core body temperature, core body temperature fluctuations, mean skin temperature, sternal sweat rate, laboratory hot flash counts (sternal skin conductance), plasma 3-methoxy-4-hydroxyphenylglycol. RESULT(S) The E(2) group had significant increases in plasma E(2) (8 +/- 2 vs. 132 +/- 22 pg/mL) and core body temperature sweating threshold (37.98 +/- 0.09 vs. 38.14 +/- 0.09 degrees C) and decreases in plasma FSH (58.8 +/- 8.9 vs. 40.1 +/- 7.6 mIU/mL) and hot flashes (1.4 +/- 0.5 vs. 0.6 +/- 0.6). These changes did not occur in the placebo group. There were no significant changes in any other measure. CONCLUSION(S) E(2) ameliorates hot flashes by raising the core body temperature sweating threshold, but does not affect core temperature fluctuations or plasma 3-methoxy-4-hydroxyphenylglycol.