from 0.002% to 0.003%. Since not all adults seeking hormone treatment and surgical reas-
signment attend specialty clinics, these rate s are likely modest underestimates. Sex differ-
ences in rate of referrals to specialty clinics vary by age group. In children, sex ratios of
natal boys to girls range from 2:1 to 4.5:1. In adolescents, the sex ratio is close to parity; in
adults, the sex ratio favors natal males, with ratios ranging from 1:1 to 6.1:1. In two coun-
tries, the sex ratio appears to favor nata l females (Japan: 2.2:1; Poland: 3.4:1). 
Development and Course