Anatomy

Cancer

Internal medicine

Endocrinology

Vellus hair

Aromatase

Hair loss

Estrogen

Hair follicle

Androgen

Scalp

Luteinizing hormone

Prolactin

Testosterone (patch)

Dihydrotestosterone

Prostate cancer

Dermal papillae

Male-pattern baldness

Hair cycle

Breast cancer

Genetics

Androgen receptor

Hormone

Medicine

Biology

International Journal of Molecular Sciences

The hair cycle and hair follicle structure are highly affected by various hormones. Androgens—such as testosterone (T); dihydrotestosterone (DHT); and their prohormones, dehydroepiandrosterone sulfate (DHEAS) and androstendione (A)—are the key factors in terminal hair growth. They act on sex-specific areas of the body, converting small, straight, fair vellus hairs into larger darker terminal hairs. They bind to intracellular androgen receptors in the dermal papilla cells of the hair follicle. The majority of hair follicles also require the intracellular enzyme 5-alpha reductase to convert testosterone into DHT. Apart from androgens, the role of other hormones is also currently being researched—e.g., estradiol can significantly alter the hair follicle growth and cycle by binding to estrogen receptors and influencing aromatase activity, which is responsible for converting androgen into estrogen (E2). Progesterone, at the level of the hair follicle, decreases the conversion of testosterone into DHT. The influence of prolactin (PRL) on hair growth has also been intensively investigated, and PRL and PRL receptors were detected in human scalp skin. Our review includes results from many analyses and provides a comprehensive up-to-date understanding of the subject of the effects of hormonal changes on the hair follicle.

Hormonal Effects on Hair Follicles