Effect of estrogen replacement therapy on bone mineral content in girls with Turner syndrome.

Because a close relationship between estrogen deficiency and osteoporosis has been proven, it is possible that lifelong estrogen deficiency might be the cause of osteopenia in Turner syndrome. This study was done to characterize the effect of estrogen therapy on bone mineralization in girls with Turner syndrome. Radial bone mineral content values were found to be below the 95% normal confidence interval in 44 of 49 untreated patients, aged 10.82 +/- 3.45 years. An inverse correlation was found between the patients' ages and their delta bone mineral content values. The effect of beginning estrogen treatment early or late was studied in 16 girls who started the treatment before and 11 who started after age 12. Although they were still deficient compared with controls, the first group had better mineralization than the second (P = .0005). Finally, nine patients were followed prospectively during replacement therapy; their bone mineral content delta values changed significantly (P = .02) during the follow-up period (3.17 +/- 0.33 years), but the bone mineral content did not normalize. Our data show that estrogen deficiency per se does not cause osteoporosis in young girls with Turner syndrome. In fact, estrogen therapy prevented bone loss but failed to normalize the low bone mineral content values. Early treatment is preferable because it reduces the bone density deficit present in untreated patients.