Prolactin levels and pituitary enlargement in hormone-treated male-to-female transsexuals.

PRL levels were evaluated during long-term treatment with cyproterone acetate 100 mg and ethinyloestradiol 100 micrograms/day orally or depot-oestrogens in 214 male-to-female transsexuals. PRL levels increased above normal in all subjects (normal less than 300 mU/l). In 46 (21.4%) subjects PRL levels rose to greater than 1000 mU/l. The incidence of PRL levels greater than 1000 mU/l was 3.7-7.2% per treatment year. Grossly elevated PRL levels were associated with high doses of oestrogens (P less than 0.05) and advanced age at the start of treatment (P less than 0.05). In 23 subjects PRL levels greater than 1000 mU/l decreased by more than 50% spontaneously (n = 5) or after dose reduction (n = 18). In five of the subgroup of 15 subjects with persistent PRL levels greater than 1000 mU/l enlargement of the pituitary gland was shown by CT-scanning. These data suggest that the lowest possible oestrogen dose and lifelong follow-up of hormone-treated male-to-female transsexuals is essential.