Thermoregulation and hormone replacement in postmenopausal women

To determine the thermoregulatory effects of hormone replacement in postmen opausal women, we measured core, skin, mean body temperatures, vasomotor ch anges, metabolic heat production, and sweat rate during warm and cold therm al challenges. The shivering to vasodilation interthreshold range was small er in women taking estrogen (0.8 +/- 0.2 degrees C) than in women taking no hormones (1.5 +/- 0.2 degrees C, P = 0.02). The vasodilation threshold was lower in the estrogen group (36.4 +/- 0.2 degrees C) than in the no hormon e (37.0 +/- 0.3 degrees C, P = 0.04) and combined estrogen/progesterone (36 .9 +/- 0.1 degrees C, P = 0.03) groups. Baseline core temperature was highe r in women on combined estrogen/progesterone therapy (37.5 +/- 0.1 degrees C) compared to those on no hormones (37.0 +/- 0.2 degrees C, P = 0.02) or e strogen alone (36.9 +/- 0.1 degrees C, P = 0.004). Estrogen therapy in post menopausal women lowers heat response thresholds and narrows the interthres hold response range for thermoregulation. Adding progesterone to estrogen t herapy elevates the heat response thresholds and increases core temperature setpoint. (C) 2000 Elsevier Science Ltd. All rights reserved.