Hormonal Effects on Hair Follicles

Abstract

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.

Alopecia and Clinical Presentation of Endocrinopathies: Pathogenetic and Diagnostic Aspects

“…Эстрадиол изменяет метаболизм андрогенов в пилосебацейном комплексе, который сам по себе демонстрирует заметную активность ароматазы -ключевого фермента в преобразовании андрогенов в эстрадиол. Кроме того, эстрадиол способен влиять на метаболизм андрогенов посредством ингибирования активности ароматазы, которая определяет превращениеандрогенов тестостерона и андростендиона в эстрогены эстрадиол и эстрон [8] То есть, ВФ одновременно является мишенью для эстрогенов и их источником [9]. Считается, что эстрогены положительно влияют на пролонгацию фазы роста волос путем связывания с локально экспрессированными рецепторами эстрогена, стимулируя синтез гликозаминогликанов, эластина, коллагена в коже [10].…”

Adipokines in the Skin and in Dermatological Diseases

“…This life-long cycling consists of growth ("anagen"), regressive ("catagen"), and quasi-quiescent ("telogen") phases [114]. Obviously, both the hair cycle and the hair growth are under tight and quite complex neuroendocrine control [115][116][117], and, of great importance, adipokines were also shown to contribute to this regulation. Indeed, by using immunohistochemistry, leptin expression was demonstrated in the hair matrix, in the inner root sheath, as well as in the dermal papilla (DP) fibroblasts of human HFs, while its receptor (long isoform) was only found to be expressed by DP fibroblasts [118].…”

Activation of Hair Cell Growth Factors by Linoleic Acid in Malva verticillata Seed

“…Hair loss depends on the rate balance between the hair growth cycle and hair loss [ 3 ]. Various factors, such as genetic factors, excessive male hormones, sebum content, and aging, are also involved in abnormal hair loss [ 4 , 5 ].…”

“…Hair is growing in hair follicle cells and undergoes a repetitive growth cycle following four stages: anagen, catagen, telogen, and exogen [ 5 , 6 , 7 ]. The duration of this growth cycle varies depending on the local site and density of hair follicles, and typically it lasts for 2 to 8 years [ 8 ].…”