BACKGROUND: Testosterone is an important anabolic hormone in humans and in vitro testosterone stimulates growth of lung and colon cancer cells. We tested the hypothesis that plasma testosterone associate with increased risk of cancer and with increased risk of early death after cancer.

MATERIALS AND METHODS: Plasma testosterone was measured in 8771 20- to 94-year-old men and women who participated in a prospective study of the general population. Participants were included in 1981-1983 and followed for a median of 22 years (range: 0-30 years).

RESULTS: During follow-up, 1140 men and 809 women developed cancer. For risk of early death after cancer, for men, after adjustment for age at diagnosis, tumour stage at diagnosis, and time since blood-sampling, the hazard ratio was 1.30 [95% confidence interval (CI) 1.03-1.65] for the 2nd quintile, 1.31 (1.02-1.67) for the 3rd quintile, 1.52 (1.19-1.93) for the 4th quintile, and 1.52 (1.20-1.91) for the 5th quintile, versus the 1st quintile. For women, corresponding hazard ratios were 1.09 (0.81-1.46), 1.17 (0.86-1.59), 1.03 (0.76-1.39), and 1.80 (1.32-2.46). For risk of cancer, multifactorially adjusted hazard ratios for risk of any cancer were 1.07 (95% CI 0.98-1.18) and 1.06 (0.93-1.22) for men and women, respectively, when testosterone doubled. For both men and women, a doubling of testosterone was not associated with risk of any cancer type.

CONCLUSIONS: In this prospective study of 8771 men and women from the general population followed for >30 years, increased levels of testosterone were associated with a 30%-80% increased risk of early death after cancer, but unchanged risk of incident cancer.