Pathophysiology and Treatment of Menopausal Hot Flashes

Robert R. Freedman, PhD

Disclosures

Semin Reprod Med. 2005;23(2):117-125. 

In This Article

Abstract and Introduction

Abstract

Hot flashes are the most common symptom of menopause. Although the appearance of hot flashes coincides with estrogen withdrawal, this does not entirely explain the phenomenon because estrogen levels do not differ between symptomatic and asymptomatic women. Luteinizing throughout? hormone pulses do not produce hot flashes nor do changes in endogenous opiates. Recent studies suggest that hot flashes are triggered by small elevations in core body temperature (Tc) acting within a reduced thermoneutral zone in symptomatic postmenopausal women. This narrowing may be due to elevated central noradrenergic activation, a contention supported by observations that clonidine and some relaxation procedures ameliorate hot flashes. Because hot flashes are triggered by Tc elevations, procedures to reduce Tc, such as lowering ambient temperature, are beneficial. Estrogen ameliorates hot flashes by increasing the Tc sweating threshold, although the underlying mechanism is not known. Recent studies of hot flashes during sleep call into question their role in producing sleep disturbance.

Introduction

Hot flashes are the most common symptom of the climacteric and occur in most postmenopausal women. The Massachusetts Women's Health Study[1] found that 75% of women surveyed reported having hot flashes in the period between peri- and postmenopause, an average of 3.8 years. Feldman[2] reported that 64% of perimenopausal women experienced hot flashes for 1 to 5 years and Kronenberg[3] reported the average duration of symptoms to be 4 years.

Of the symptomatic women in Kronenberg's study,[3] 87% reported daily hot flashes and one third of those reported more than 10 per day. Hot flashes usually lasted 1 to 5 minutes, with a small percentage persisting for more than 6 minutes. The experience of a hot flash was usually described as sensations of intense heat, sweating, flushing, chills, and clamminess. Sweating was reported most frequently in the face, neck, and chest, but rarely caudally.

There are few major risk factors for menopausal hot flashes. Two recent investigations[4,5] have found that high body mass index is directly related to hot flash frequency. This may be due to the effect of increased insulation from body fat, resulting in elevated core body temperature, which triggers hot flashes.[6] Cigarette smoking has also been found to increase the risk of hot flashes,[4,5] possibly through the effect on estrogen metabolism or through the thermogenic effects of nicotine.[7]

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