Grey Hair and Stress: Not Just Age
Melanocytes are cells that specialize in producing melanin pigments, responsible for the color of the skin and hair. They are typically located in the basal layer of the epidermis and in hair follicles where they are originated from a population of stem cells, known as melanocyte stem cells.
However, the coloration of hair and skin is not determined by the number of melanocytes, but by how active these cells are. Melanin is packaged and delivered to keratinocytes (another type of skin cells) by melanosomes whose formation, maturation, and trafficking are crucial to pigmentation, and therefore, defects in this process lead to depigmentation [1].
Stress and Grey hair
Although hair greying is associated with aging due to the gradual decrease in the number of newly generated melanocytes from melanocyte stem cells, stress has also been shown to play a role in this process.
Noradrenaline (norepinephrine) is a neurotransmitter secreted by the adrenal medulla and the sympathetic nerves in response to stress by increasing arousal and alertness, promoting vigilance, and enhancing memory formation and retrieval.
Recently, a link between Noradrenaline and hair greying was established. The study showed that Noradrenaline causes a loss of melanocyte stem cells leading to hair greying. As sympathetic nerves extend to hair follicles, their release of noradrenaline in response to stress leads to increased differentiation of melanocytes stem cells into melanocytes and their migration away from their reserve in the hair follicle.
Therefore, this noradrenaline-dependent change results in a decreased release of new pigment cells, and thus, new hair becomes grey, and then white [2].
Conclusion
Hair greying is associated with age and is also due to stress conditions that result in the secretion of noradrenaline by sympathetic nerves into hair follicles, leading to the migration of melanocytes stem cells away from their reserve in the hair follicle.
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