Hormonal Effects on Hair Follicles.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic biological pathways without systematic methodology
PubMed 32731328 · doi:10.3390/ijms21155342
What was done
This review summarized current literature regarding how various hormones affect hair follicle structure and the hair growth cycle. It focused on the mechanistic pathways of androgens (testosterone, dihydrotestosterone, dehydroepiandrosterone sulfate, androstenedione), estrogens (estradiol), progesterone, and prolactin in dermal papilla cells and scalp tissue.
What was found
The abstract reports no quantitative metrics, effect sizes, or sample statistics. Descriptively, androgens convert vellus hairs to terminal hairs in sex-specific body areas via dermal papilla androgen receptors, typically requiring 5-alpha reductase conversion of testosterone to DHT. Estradiol alters follicle growth through estrogen receptors and aromatase activity; progesterone inhibits follicular conversion of testosterone to DHT; and prolactin and prolactin receptors are expressed in human scalp skin.
Why it matters
The paper synthesizes physiological pathways that explain endocrine influence on hair growth and loss, framing potential therapeutic targets for hormone-associated hair disorders.
Limits
The abstract describes a non-systematic narrative review with no defined search protocol, study selection criteria, or quantitative synthesis. No primary human clinical data or statistical outcomes are reported in the abstract.
Cited by
- supports The scalp skin has a high density and expression of 5-alpha reductase enzymes that locally convert testosterone to dihydrotestosterone (DHT).