TLDR Androgens can both promote and prevent hair growth due to differences in gene expression in hair follicles.
The document from January 1, 2000, examines the contradictory effects of androgens on hair growth, noting that androgens can both stimulate hair growth in certain body areas and cause hair loss on the scalp, a condition known as androgenetic alopecia. It identifies the dermal papilla as the key site of androgen action, where androgens bind to receptors and influence the production of paracrine factors. Studies showed that dermal papilla cells from androgen-sensitive areas have androgen receptors and vary in their ability to form 5α-dihydrotestosterone (DHT), which correlates with hair growth patterns seen in individuals with 5α-reductase deficiency. The document suggests that the differences in hair follicle responses are due to differential gene expression, likely established during embryogenesis. It also discusses the role of paracrine factors and the SCF/KIT pathway in hair follicle behavior, and how these findings could inform treatments for hair disorders related to androgen levels.
231 citations,
December 1999 in “Journal of Investigative Dermatology” Hair follicle size is mainly influenced by the number of cells and extracellular matrix volume, with cell number having a larger impact.
51 citations,
November 1998 in “The journal of investigative dermatology/Journal of investigative dermatology” Beard cells, unlike scalp cells, produce growth factors in response to testosterone, which may explain differences in hair growth.
173 citations,
July 1995 in “Biochemical and biophysical research communications” Male hormones promote hair cell growth by using a growth factor from nearby skin cells.
6 citations,
January 2022 in “Journal of Investigative Dermatology” Male pattern baldness is linked to higher levels of a certain receptor in the scalp, which leads to the shrinking of blood vessels and hair loss. Early treatment targeting this receptor could be more effective.
January 2015 in “American journal of medical and biological research” 
122 citations,
November 2010 in “Journal of Dermatological Science” Male pattern baldness involves hormones and cell signals affecting hair growth.
11 citations,
January 2010 in “Springer eBooks” 
229 citations,
August 2002 in “Experimental Gerontology” AGA causes hair loss by shrinking hair follicles due to DHT binding, and can be treated with finasteride and minoxidil.
66 citations,
January 2000 in “Hormone Research in Paediatrics” Androgens can both promote and prevent hair growth due to differences in gene expression in hair follicles.
227 citations,
January 1998 in “Journal of Endocrinology” Cells from balding scalps have more androgen receptors than cells from non-balding scalps.
124 citations,
April 1992 in “Journal of Endocrinology/Journal of endocrinology” Beard hair follicles have more androgen receptors than non-balding scalp hair follicles.
