Hot Flashes: Physiology

hot flashes

Don’t blame the messenger! The physiological mechanisms of hot flashes are unknown. However, we have some clues that they are linked to 1) thermoregulatory disruption; and 2) neurochemical disruption.

Thermoregulatory Disruption: Hot flashes have been described to be an exaggerated response to changes in the thermoregulatory system. What does that mean? Thermoregulation maintains your body temperature. Did you know that the threshold point between sweating and shivering can occur with a 0.4 degree (C) change in internal temperature: Sweating happens at higher-than threshold temperatures, with shivering at lower temperatures. In individuals with hot flashes, this thermoregulatory system is disrupted. This disruption may be due to changes in neurochemicals such as estrogen, norepinephrine, serotonin, glucose, and others.

Neurochemical Disruption: Estrogen is a strong suspect neurochemical linked to hot flashes. Unfortunately, while estrogen is the most effective drug intervention for hot flashes, we cannot offer it is your cancer is hormone-dependent. Estrogen appears to stabilize thermoregulatory disruption. It may reduce spontaneous fluctuations in core boy temperature after ovary removal. Estrogen therapy raises the sweating threshold.

But could it be that estrogen works via other chemicals? For example, changes in estrogen levels alter levels of the brain chemicals norepinephrine and serotonin. Drugs (such as clonidine) that activate norepinephrine can alleviate hot flashes. Drugs (such as  yohimbine) that block norepinephrine can exacerbate the symptoms. Around menopause, serotonin levels are positively correlated to hot flashes. Low blood sugar levels (hypoglycemia) may trigger hot flashes. Eating may provide an average of 90 minutes free from hot flashes.

We will turn to the management of hot flashes in the next blog. Thanks for hanging in there through the biochemistry-speak! I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

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Reference: Fisher WI et al. CA: A Journal for Clinicians, vol 63 (3).

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