Scalp hair parameter changes in transgender individuals commencing gender-affirming hormone therapy: A 24-week prospective observational study

To the Editor: Sex steroids (androgens and estrogens) can influence hair growth by regulating the lower portion of the hair bulb during the hair cycle, thereby influencing hair diameter, growth rate, and length. On the human scalp, androgens can shorten the anagen phase and telogen phase whereas estrogens are proposed to prolong anagen and inhibit catagen. In transgender (trans) people, masculinizing hormone therapy (MHT) with testosterone is known to induce androgenetic alopecia (AGA), and feminizing hormone therapy (FHT) with estradiol and antiandrogens improves hirsutism. Studies with objective outcomes of scalp hair are lacking...