When you compare pictures of presidents who do not alter their hair color, they all leave office considerably grayer than when they started, which some link to the stress of the office.

Marie Antoinette syndrome is a condition in which scalp hair suddenly turns white. The name comes from the story that Marie Antoinettes hair turned white the night before she was to face the guillotine during the French Revolution.

The same thing happened to survivors of atomic bomb attacks during World War II. It has long been thought that genetics, aging and stress all contribute to developing gray hair.

New research has revealed how stress contributes to graying.

On average, humans have 100,000 hair follicles in their scalp, which produce hairs of one color or another. Hair color is determined by the types of melanin produced by cells called melanocytes. Melanocytes grow from melanocyte stem cells (MeSCs) inside the hair follicle.

With age, the number of MeSCs declines, leading to hair graying in stages from the occasional gray one, to salt and pepper, to gray and then white when all the MeSCs are gone. But how stress leads to gray hair has been a mystery.

It had been thought that stress-induced graying involved hormones such as corticosterone or autoimmune reactions. Scientists did experiments in mice and found that neither of those was the cause.

However, when they blocked the receptor for the fight-or-flight hormone, noradrenaline, they stopped hair graying in response to stress in mice. Finally, they had a clue.

The main source of noradrenaline is the adrenal glands. However, when the scientists removed the adrenal glands in mice, their hair still turned gray in response to stress. Another source of the hormone is the sympathetic nervous system (SNS), which is part of the autonomic nervous system that works to regulate many functions and parts of the body without us thinking about it.

The SNS controls the fight-or-flight response to stress to prepare the whole body for physical activity. SNS nerves and MeSCs are close together in the hair follicle, and blocking those SNS nerves prevented the hairs from turning gray in response to stress. Conversely, when the SNS nerves were over-activated, the mice went gray even without stress.

Normally, MeSCs are dormant unless hair is regrowing. In response to extreme stress, MeSCs reproduce and mature into melanocytes quickly. Large numbers of melanocytes then migrate from the follicle, leaving no MeSCs in the follicles and no melanocytes to provide the pigments that give hair its color. Once they are all gone, hair will never be its original color again.

This brings up the added question about other effects of stress, including a decline in immunity and the ability to fight off infections.

The SNS system also stimulates stem cells in the bone marrow to mature into the blood cells required to protect us from infections. Nearly every organ in the body contains stem cells, and stress could have an impact on those as well.

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at http://www.medicaldiscoverynews.com.

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How stress contributes to the graying of hair - Galveston County Daily News

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