TLDR Testosterone can slow down hair growth when combined with certain cells from bald scalps, and this effect can be blocked by an androgen receptor blocker.
In 1996, a study was conducted to understand the role of testosterone in hair growth inhibition using dermal papilla cells from the bald scalps of postpubertal stumptailed macaques. The study found that testosterone did not affect the proliferation of dermal papilla cells or outer root sheath cells when cultured separately. However, when co-cultured, testosterone inhibited the proliferation of outer root sheath cells, but only when the dermal papilla cells were from the bald scalps of adult macaques. This inhibition did not occur with dermal papilla cells from the hairy scalps of adult macaques or the pre-bald scalps of juvenile macaques. The study also discovered that RU 58841, an androgen receptor blocker, antagonized the testosterone-induced inhibition, suggesting that androgens may play a crucial role in hair growth and baldness. The study concluded that testosterone's inhibitory effect on epithelial cell proliferation is age-dependent and may involve the induction of repressors or growth factors from dermal papilla cells.View this study on academic.oup.com →
Finasteride increases hair growth, prolongs hair cycle, and lowers dihydrotestosterone levels.
RU 58841 may treat acne, hair loss, and excessive hair growth.