Postmenopausal Physiological Changes
The hallmark of menopause is the marked reduction of estradiol levels due to ovarian failure. This, among other factors result in hot flashes, the most common menopausal symptom. Hot flashes (HFs) can be measured objectively, both inside and outside the laboratory, using sternal skin conductance, an electrical measure of sweating. We have found that HFs are triggered by small elevations in core body temperature (T C ), acting within a greatly reduced thermoneutral zone. This reduction is caused by elevated central sympathetic activation, among other factors. There is a circadian rhythm of HFs peaking at 1825 h. Imaging studies have shown that hot flash activation begins in the brainstem, followed by the insula and by the prefrontal cortex. HFs in the first, but not the second half of the night can produce awakenings and arousals. This is because rapid eye movement (REM) sleep suppresses thermoregulatory effector responses, which include hot flashes.
KeywordsHot flash Menopause Sleep Thermoregulation
This work was supported by NIH Merit Award, R37-AG05233 and by R01-MH63089.
- Askel S, Schomberg DW, Tyrey L et al (1976) Vasomotor symptoms, serum estrogens, gonadotropin levels in surgical menopause. Am J Obstet Gynecol 126:165–169Google Scholar
- Brück K, Zeisberger E (1990) Adaptive changes in thermoregulation and their neuropharmacological basis. In: Schönbaum E, Lomax P (eds) Thermoregulation: physiology and biochemistry. Pergamon, New York, pp 255–307Google Scholar
- Diwadkar VA, Murphy ER, Freedman RR (2013) Temporal sequencing of brain activations during naturally occurring thermoregulatory events. Cereb cortex Jun 19 [Epub ahead of print]Google Scholar
- Freedman RR (2009) Patient satisfaction with miniature, ambulatory, postmenopausal hot flash recorder. Open Med Devices J 1:1–2Google Scholar
- Freedman RR, Woodward S (1995) Altered shivering threshold in postmenopausal women with hot flashes. Menopause 2:163–168Google Scholar
- Freedman RR, Woodward S, Norton D (1992) Laboratory and ambulatory monitoring of menopausal hot flushes: comparison of symptomatic and asymptomatic women. J Psychophysiol 6:162–166Google Scholar
- Insel PA, Motulsky HJ (1987) Physiologic and pharmacologic regulation of adrenergic receptors. In: Insel PA (ed) Adrenergic receptors in man. Marcel Dekker, New York, pp 201–236Google Scholar
- Kopin IJ, Blombery P, Ebert MH et al (1984) Disposition and metabolism of MHPG-CD3 in humans: plasma MHPG as the principal pathway of norepinephrine metabolism and as an important determinant in CSF levels of MHPG. In: Usdin E et al (eds) Frontiers in biochemical and pharmacological research in depression. Raven, New York, pp 57–68Google Scholar
- Molnar GW (1975) Body temperature during menopausal hot flashes. J Appl Physiol: Respir Environ Exerc Physiol 38:499–503Google Scholar
- North American Menopause Society (2007) Menopause practice: a clinician’s guide. Normal physiology, pp 19–27Google Scholar