[Osteo-anabolic estrogen therapy in a transsexual man]

A 31-year-old man presented at the endocrinology out-patient clinic for the initiation of sex-change treatment. His manifestly transsexual male-to-female appearance was confirmed by a psychiatric-sexological expert report. The patient had been living as a woman for one year. Physical examination showed normal male physique with typical secondary hair growth and normal male genitals.

The serum testosterone level was at the upper limits of normal, that for oestrogen at the lower limit. Bone densitometry showed bone density at the upper limit of normal. Other laboratory tests were unremarkable.

During 30 months on cyproterone, 100 mg daily, bone mass fell at the rate of 5% per year. Bone biopsy revealed high turnover osteoporosis. Bone mass rose by 4% per year after the additional oral intake of oestradiol valerate, 2 mg daily. Osteoblastic cells, isolated from part of the biopsy tissue, with the patient's consent, was found to be stimulated by oestradiol in vitro.

The described bone mass changes indicate the important role played by sex hormones in the maintenance of bone mass acquired during adolescence. The findings confirm that in males not only testosterone but also oestrogens has an anabolic effect on bone.