Effects of sex steroids on components of the insulin resistance syndrome in transsexual subjects

OBJECTIVE: Sex differences are found in most components of the insulin resistance syndrome and the associated cardiovascular risk profile. These differences are attributed to sex-specific sex steroid profiles, but the effects of sex steroids on the individual components of the insulin resistance syndrome remain incompletely understood.

DESIGN: Prospective, intervention study.

SUBJECTS: In 37 young (age range 16-36 years), nonobese [body mass index (BMI) < 29], transsexual subjects, effects of ethinyl oestradiol (100 micro g/day) + cyproterone acetate (100 mg/day) administration were evaluated in 20 male-to-female transsexuals and of testosterone-ester administration [250 mg intramuscularly (i.m.)/2 weeks] in 17 female-to-male transsexuals.

MEASUREMENTS: We studied lipid spectrum, postheparin hepatic lipase (HL) and lipoprotein lipase (LPL) activity, blood pressure, glucose utilization (by euglycaemic hyperinsulinaemic clamp), and fat areas (by magnetic resonance imaging) at baseline and during 1-year cross-sex hormone administration.

RESULTS: Oestrogens + antiandrogens increased high-density lipoprotein (HDL)-cholesterol and decreased LDL-cholesterol, and HL activity, which are considered beneficial. But this combination also increased triglycerides, blood pressure, subcutaneous fat and visceral fat, and decreased the LDL-particle size, LPL activity and insulin sensitivity, which are all considered detrimental. Testosterone reduced HDL-cholesterol and the LDL-particle size, and increased triglycerides and HL activity. An android fat distribution was induced (i.e. decreased subcutaneous and increased visceral fat). Blood pressure, total and LDL-cholesterol, LPL activity and insulin sensitivity were mainly unaffected.

CONCLUSIONS: The effects of cross-sex hormone treatment - in the dosages used in this study - in healthy, nonobese, young transsexual subjects do not show unequivocally that female sex steroids, given in large amounts to male subjects, have beneficial effects on cardiovascular profile and that high dose testosterone administration to female subjects is detrimental with respect to cardiovascular risk.