The effects of long-term testosterone therapy on insulin, SHBG, and IGF-I levels in female transsexuals

Abstract

Serum levels of testosterone (T), insulin, sex hormone-binding globulin (SHBG) and insulin-like growth factor-I (IGF-I) were measured in two groups of female transsexuals. Group 1, a control group, consisted of 14 normal menstruating pre-operated female transsexuals who have had no previous history of hormone therapy. Group 2, 16 transsexuals who had successfully gone through their sex reassignment operations, comprising total hysterectomy, bilateral oophorectomy, and the construction of a neophallus 1 to 11 years ago. They had been on long-term testosterone therapy, 250 mg monthly intra-muscular injection of testosterone esters (a depot preparation, Sustanon-250, Organon, OSS, The Netherlands), for an average duration of 33 months before they were recruited into the study. The median (25th-75th centile range) level of testosterone in female transsexual controls (Group 1) was low, 0.48 (0.38-0.62) ng/ml, while that for subjects in Group 2 was 6.0 (2.8-8.3) ng/ml. The levels of SHBG in Group 2 (mean±SE=32.5±3.0 nmol/l) were significantly reduced (P=0.0001) as compared to corresponding levels in Group 1 (mean±SE = 72.2±4.8 nmol/l). On the other hand, serum levels of insulin were significantly higher (P= 0.0001) in androgenized castrated transsexuals of Group 2 than corresponding levels in subjects of Group 1. IGF-I levels in androgenized females of Group 2 were not significantly different from those in pre-treated female transsexuals. Levels of SHBG were significantly and negatively correlated to corresponding levels of insulin (P