['Although obesity is associated with gonadal dysfunction in the general population, gonadotoxic treatment might diminish the impact of obesity in childhood cancer survivors (CCS). The aim was to evaluate whether altered body composition is associated with gonadal dysfunction in male CCS, independent of gonadotoxic cancer treatment.', 'Three hundred fifty-one male CCS were included. Median age at diagnosis was 5.9 years (0-17.8) and median age at follow-up 25.6 years (18.0-45.8). Total and non-SHBG-bound testosterone, sex hormone-binding globulin, inhibin B, and follicle-stimulating hormone (FSH) were studied. Potential determinants were BMI, waist circumference, waist-hip ratio, and body composition measures (dual energy X-ray absorptiometry).', 'Non-SHBG-bound testosterone was significantly decreased in survivors with BMI ≥ 30 kg/m(2) (adjusted mean 9.1 nmol/L vs. 10.2 nmol/L, P = 0.015), high fat percentage (10.0 vs. 11.2, P = 0.004), and high waist circumference (>102 cm) (9.0 vs. 11.0, P = 0.020). Survivors with high fat percentage (≥25%) had significantly lower inhibin B/FSH ratios (inhibin B/FSH ratio: β -34%, P = 0.041).'] Does obesity independently influence gonadal function in very long-term adult male survivors of childhood cancer?