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

Abstract 

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 17β-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 E₂ group had significant increases in plasma E₂ (8 ± 2 vs. 132 ± 22 pg/mL) and core body temperature sweating threshold (37.98 ± 0.09 vs. 38.14 ± 0.09°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): E₂ ameliorates hot flashes by raising the core body temperature sweating threshold, but does not affect core temperature fluctuations or plasma 3-methoxy-4-hydroxyphenylglycol.

Keywords:  Estrogen, hot flashes, sweating threshold, thermoregulation