Testosterone concentrations in young pubertal and post-pubertal obese males

Objective Obesity in adult males is associated with hypogonadotropic hypogonadism. We evaluated the effect of obesity on plasma testosterone concentrations in pubertal and post-pubertal young males. Design and methods Morning fasting blood samples were obtained from 25 obese [body mass index (BMI) 95th percentile] and 25 lean (BMI <85th percentile) males between the ages 1420years with Tanner staging 4. Total (TT) and free testosterone (FT) and estradiol concentrations were measured by liquid chromatography tandem mass spectrometry and equilibrium dialysis. Free testosterone was also calculated using SHBG and albumin. C-reactive protein (CRP), insulin and glucose concentrations were measured and homoeostasis model of insulin resistance (HOMA-IR) was calculated. Results After controlling for age and Tanner staging, obese males had a significantly lower total testosterone (10 center dot 5 vs 21 center dot 44nmol/l), free testosterone (0 center dot 22 vs 0 center dot 39nmol/l) and calculated free testosterone (0 center dot 26 vs 0 center dot 44nmol/l) concentrations as compared to lean males (P<0 center dot 001 for all). Obese males had higher CRP concentrations (2 center dot 8 vs 0 center dot 8mg/l; P<0 center dot 001), and HOMA-IR (3 center dot 8 vs 1 center dot 1; P<0 center dot 001) than lean males. Free testosterone concentrations were positively related to age and negatively to BMI, HOMA-IR and CRP concentrations. Total and free estradiol concentrations were significantly lower in males with subnormal testosterone concentrations. Conclusion Testosterone concentrations of young obese pubertal and post-pubertal males are 4050% lower than those with normal BMI. Obesity in young males is associated with low testosterone concentrations, which are not secondary to an increase in estradiol concentrations. Our results need to be confirmed in a larger number of subjects.