XVII Harry Benjamin International Gender Dysphoria Association Symposium
31 October - 4 November 2001, Galveston, Texas, U.S.A.

Effects of Testosterone Therapy on Bone Mineral Density in the FTM Patient

TANGPRICHA, VIN U.S.A.
Co-authors: Adrian Turner, Alan Malabanan & Michael Holick (U.S.A.)
E-mail: vin@bu.edu

Background: The effects of androgens on the female to male transsexual skeleton are not clearly defined. There are limited studies investigating the effects of testosterone on bone mineral density (BMD) in these patients. One previous study in 19 female to male transsexual patients revealed a statistically significant decrease of 4.5% over 3.5 years in bone mineral density at the lumbar spine after treatment with testosterone and after total hysterectomy. The objective of this study is to determine the effects of testosterone on BMD and markers of bone turnover in FTM transsexual patients. We obtained approval for the study from our institutional review board (IRB). Patients were informed about the study by their endocrinologists. We started recruitment of subjects in July 2000. We obtained written informed consent from each patient. All female to male transsexual patients were eligible for the study, including those who had already initiated testosterone therapy. Baseline urine N-telopeptide and bone mineral density (BMD) were obtained at the femoral neck and lumbar spine. Bone mineral density will be determined annually and serum studies will be determined semi-annually for 2 years.

Results: We have enrolled 10 patients into our study. Four patients enrolled after initiation of testosterone therapy and six enrolled prior to initiation of testosterone therapy. The average age for the patients on testosterone and those who have not yet started testosterone was 40 and 30, respectively. On average, the patients who were on testosterone were treated for 4 years. The BMD at the femoral neck was statistically higher in the baseline untreated patients (1.12 gm/cm2) versus those in the testosterone treated group (0.897 gm/cm2). All of the patients treated with testosterone had osteopenia at the femoral versus 1 out of 6 in the baseline untreated group. There was no difference in spinal BMD. Osteocalcin levels were higher in the testosterone treated group versus untreated group, 6.7 ng/ml versus 3.7 ng/mo. Only one patient was vitamin D deficient (250HVD <20mg.ml). The N-telopeptide and iPTH values have not yet been determined.

Discussion: We report preliminary results of year one in our three-year study. In our preliminary analysis, all of the testosterone treated patients had osteopenia at the femoral neck. This early result may suggest that testosterone may be more sparing of trabecular bone versus cortical bone, directly or indirectly via peripheral conversion to estrogens. We are eagerly awaiting the results of bone turnover and BMD in this group of FTM patients. The final analysis of this study should be completed by 2002.