Background: Testosterone replacement in hypogonadal males improves body composition, sexual function and health related quality of life (HRQOL). Male cancer survivors are at risk of androgen deficiency, however, when and in whom testosterone should be replaced remain unanswered questions.

Objective: The aim of our study was to define the prevalence of androgen deficiency in this patient group through assessment of testosterone levels and related measures.

Design: This was a cross-sectional, observational study of cases and controls. We recruited 176 cancer survivors and 213 controls, aged 25 to 45 years.

Results: Ninety-seven percent of cancer survivors had received chemotherapy and 40% radiotherapy. Cancer survivors had lower tT levels than controls (mean difference 2.67 nmol/l, 95% CI 1.58-3.76, p=0.003), and 24/176 (13.6%, 95% CI: 9.3 to 19.5) had a tT <10 nmol/l, which was <2.5% centile for controls. Cancer survivors had a greater fat mass, higher fasting insulin and glucose levels, increased fatigue, and reduced sexual function and HRQOL. In both cohorts, the tT correlated negatively with insulin levels and negatively with body fat mass; however the difference in tT between them was independent of fat mass. We measured tT and SHBG and calculated bioavailable testosterone. The changes in calculated bioavailable testosterone were similar to tT.

Conclusions: A significant proportion of young male cancer survivors had a frankly low tT associated with an increased fat mass and insulin level compared to controls. These factors would be predicted to improve in response to testosterone replacement therapy and provide a powerful argument for an interventional study of testosterone therapy in young male cancer survivors.