5α-Reductase isozymes and aromatase mRNA levels in plucked hair from young women with female pattern hair loss. https://www.ncbi.nlm.nih.gov/pubmed/29185104 Female pattern hair loss (FPHL) is an important hair disorder, especially when young women are affected. However, pharmacological treatments are not successful in all women. Androgens, especially dihydrotestosterone (DHT), may play a role in FPHL, but many women with this disorder have normal serum androgen levels. It therefore appears that hair follicle levels of DHT depend on in situ testosterone (T) metabolism. Because T can be converted to DHT or estradiol (E2) by 5α-reductase (5α-R) and aromatase, respectively, these enzymes would determine DHT and E2 concentrations and their ratio. We propose and apply a low-invasive, sensitive and precise method for the absolute quantification of mRNA levels of aromatase and 5α-R isozymes (type 1, type 2 and type 3) in plucked hair from young women with FPHL. Normoandrogenic women with FPHL and controls were studied. Plucked hair samples were obtained by trichogram from vertex scalp and mRNA levels quantified by real-time RT-PCR. We revealed for the first time the presence of 5α-R3 mRNA in human hair. Interestingly, one, two, or even three 5α-R isozymes were increased in some women with FPHL but not in others, which may explain the lack of response to 5α-R inhibitors in some FPHL cases. Aromatase mRNA levels were significantly lower in women with FPHL than in controls. It may therefore produce a reduction in oestrogen levels and an increase in the androgen/oestrogen ratio in hair. The proposed low-invasive technique offers a molecular aetiologic diagnosis of FPHL for the selection of more appropriate pharmacological treatments with early predicted effectiveness.