In M→F transsexuals, the pilosebaceous unit was inhibited in its function on estrogen plus antiandrogen administration, as has been shown in hirsute women (
7,
27). Estrogen plus antiandrogen administration decreases hirsutism scores, hair growth rate, and hair density. Interestingly, the decrease in hair-shaft diameter had already reached its maximum after 4 months and did not progress any further. Similar changes, over time, were found in hair growth measurements on the abdomen (as a measure of the truncal hair growth) and on the cheek (as a measure of facial hair growth), as evidenced by strong intercorrelations (Table 3
⇑). The clinical observation that beard growth, as compared with the hair growth on the abdomen, is relatively resistant to androgen suppression may be explained by the larger facial hair density and hair-shaft diameter, and, therefore, most patients find facial hair reduction upon androgen deprivation rather slow. Remarkably enough, whereas androgen deprivation led to a decrease of hair diameter, growth of hair length was relatively preserved, pointing to a differential regulation of growth of hair length and hair width. Although skin sebum production dropped quickly to almost undetectable levels, male hair growth nevertheless remained substantial (even after 12 months), in spite of the rapid and considerable suppression of androgenicity in M→F transsexuals. Thus, circulating androgens do not seem necessary to sustain some degree of male hair growth once it has been established. This is consistent with our clinical observation in M→F transsexuals, who (years after orchiectomy) continue to have beard growth, with thinner hairs though.
