Biochemical, metabolic, and vascular mechanisms in menopausal hot flashes.
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.


METHODS
Laboratory physiological study.


METHODS
University medical center.


METHODS
Fourteen healthy, postmenopausal women reporting frequent hot flashes.


METHODS
Data were recorded for 3 hours in a temperature- and humidity-controlled room.


METHODS
Core body temperature, mean skin temperature, respiratory exchange ratio, sternal skin conductance, plasma 3-methoxy-4-hydroxyphenylglycol, and vanillylmandelic acid.


RESULTS
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.


CONCLUSIONS
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.
Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan, USA. aa2613@wayne.edu
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Freedman
D000704:Analysis of Variance; D001833:Body Temperature Regulation / Q000502:physiology*; D005260:Female; D005712:Galvanic Skin Response; D019584:Hot Flashes / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008593:Menopause / Q000502:physiology*; D008875:Middle Aged; D009638:Norepinephrine / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*
D009638:Norepinephrine