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Biochemical, metabolic, and vascular mechanisms in menopausal hot flashes
1Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan, USA. aa2613@wayne.edu
Objective:
To determine if increases in core body temperature preceding most hot flashes are caused by increased metabolic rate, peripheral vasoconstriction, or central noradrenergic activation.
Design:
Laboratory physiological study.
Setting:
University medical center.
Patient(S):
Fourteen healthy, postmenopausal women reporting frequent hot flashes.
Intervention(S):
Data were recorded for 3 hours in a temperature- and humidity-controlled room.
Main Outcome Measure(S):
Core body temperature, mean skin temperature, respiratory exchange ratio, sternal skin conductance, plasma 3-methoxy-4-hydroxyphenylglycol, and vanillylmandelic acid.
Result(S):
Twenty-nine physiologically defined hot flashes were recorded. Increases in core body temperature, measured with an ingested radiotelemetry capsule, preceded 76% of the flashes. Increased metabolic rate began after increased core temperature. Peripheral vasoconstriction did not occur. Plasma levels of 3-methoxy-4-hydroxyphenylglycol, a metabolite of brain norepinephrine, increased significantly, whereas vanillylmandelic acid, a peripheral metabolite, did not.
Conclusion(S):
Core body temperature elevations preceding menopausal hot flashes are not driven by peripheral vasoconstriction or increased metabolic rate, but probably by a central noradrenergic mechanism.