The effects of oestrogen exposure on bone mass in male to female transsexuals

Abstract

OBJECTIVE The importance of oestrogen on bone mineral density (BMD) in males was suggested by reports of patients with oestrogen resistance and aromatase deficiency who demonstrated osteoporosis and epiphyseal plate maturation defect despite high testosterone levels. In the present study, we examined the effects of oestrogen exposure on BMD in transsexual men. DESIGN Cross-sectional study of BMD in male to female transsexuals. PATIENTS Subjects consisted of two groups of transsexual male dancers aged 16-34 years who did not receive transsexual operations (n = 28). Group 1 (n = 11) and group 2 (n = 17) had used oestrogen for 2 years or less and more than 2 years, respectively. Twenty-four healthy adult males served as controls. RESULTS signs of feminization were presented in both group 1 and group 2, with Tanner's stage II-III breast development. BMD at various sites were correlated only to body weight and not to smoking or milk consumption. After controlling for body weight, it was found that group 2 had significantly higher BMD at L2-4 than controls (1.22 ± 0.03 vs. 1.14 ± 0.03 g/cm2, P < 0.05) and group 1 (1.22 ± 0.03 vs. 1.08 ± 0.04 g/cm2, P < 0.05). BMD at femoral neck was also higher in group 2 compared to controls (1.10 ± 0.03 vs. 1.01 ± 0.03 g/cm2, P < 0.05) and group 1 (1.10 ± 0.03 vs. 0.95 ± 0.04 g/cm2, P < 0.05). Group 1 subjects had lower BMD compared to controls at femoral trochanter (0.70 ± 0-04 vs. 0.83 ± 0.03 g/cm2, P < 0.05) and total femur (0.96 ± 0.05 vs. 1.07 ± 0.03 g/cm2 P < 0.05). CONCLUSIONS Long-term oestrogen exposure transsexual men result in an increase in bone mineral density despite signs of feminization. This suggests that oestrogen has positive effects on bone density in males. The finding of the trend towards reduced bone density in group 1 remains unexplained.