Encyclopedia Reference entry Physiology

What is cortisol?

Cortisol is a steroid hormone made by the adrenal glands. It helps regulate metabolism, blood sugar, inflammation and the body's response to stress, and its level naturally rises in the morning and falls through the day.

Cortisol and hair

Hair follicles respond to stress signals, which is why researchers study cortisol. In mice, the stress hormone corticosterone (the rodent equivalent of cortisol) kept hair-follicle stem cells in an extended resting state and delayed new growth. (Choi et al., 2021)

Laboratory work suggests human follicles may respond in similar ways, but evidence in people is still limited. (Thom, 2016)

Hair as a record of stress

Cortisol is deposited in growing hair, so hair-cortisol measurement is used in research as a marker of stress over recent months. It is a research tool, not a test for hair loss. (Russell et al., 2012)

What it means in practice

Stress-related shedding usually reflects a temporary disruption of the hair cycle rather than permanent loss. Persistent or patchy hair loss should be assessed by a dermatologist.

See also: Stress, Telogen Effluvium, Hair Cycle.

Sources

Choi S, Zhang B, Ma S, et al. Corticosterone inhibits GAS6 to govern hair follicle stem-cell quiescence. Nature. 2021;592(7854):428–32.

Russell E, Koren G, Rieder M, Van Uum S. Hair cortisol as a biological marker of chronic stress: current status, future directions and unanswered questions. Psychoneuroendocrinology. 2012;37(5):589–601.

Thom E. Stress and the hair growth cycle: cortisol-induced hair growth disruption. J Drugs Dermatol. 2016;15(8):1001–4.

Questions

Does high cortisol cause hair loss? −

Severe or prolonged stress is associated with increased shedding, and animal research shows stress hormones can hold follicles in a resting state. In people the link is real but complex, and cortisol is one factor among several.

Can you measure cortisol in hair? +

Will hair grow back after stress-related shedding? +

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