BIOCHEMICAL, METABOLIC, AND VASCULAR MECHANISMS IN MENOPAUSAL HOT FLASHES

Objective: To determine if increases in core body temperature precedin g most hot flashes are caused by increased metabolic rare, peripheral vasoconstriction, or central noradrenergic activation. Design: Laborat ory physiological study. Setting: University medical center. Patient(s ): Fourteen healthy, postmenopausal women reporting frequent hot hashe s. Intervention(s): Data were recorded for 3 hours in a temperature- a nd humidity-controlled room. Main Outcome Measure(s): Core body temper ature, mean skin temperature, respiratory exchange ratio, sternal skin conductance, plasma 3-methoxy-4-hydroxyphenylglycol, and vanillylmand elic acid. Result(s): Twenty-nine physiologically defined hot hashes w ere recorded. Increases in core body temperature, measured with an ing ested radiotelemetry capsule, preceded 76% of the flashes. Increased m etabolic rate began after increased core temperature. Peripheral vasoc onstriction did not occur. Plasma levels of 3-methoxy-3-hydroxyphenylg lycol, a metabolite of brain norepinephrine, increased significantly, whereas vanillylmandelic acid, a peripheral metabolite, did not. Concl usion(s): Core body temperature elevations preceding menopausal hot ha shes are not driven by peripheral vasoconstriction or increased metabo lic rate, but probably by a central noradrenergic mechanism. (Fertil S teril(R) 1998;70:332-7. (C) 1998 by American Society for Reproductive Medicine.).