A higher prediagnostic insulin level is a prospective risk factor for incident prostate cancer.

A higher insulin level has been linked to the risk of prostate cancer promotion. However, several reports claim that there is no association between a higher insulin level and the risk of incident prostate cancer. In the present report, the insulin hypothesis was tested once more prospectively in men with a benign prostatic disorder. Three hundred and eighty-nine consecutive patients referred with lower urinary tract symptoms without clinical prostate cancer were included during 1994-2002. Follow-up was performed in 2006. Data were obtained from the Swedish National Cancer Register and the Regional Cancer Register, Oncological Centre, Göteborg, Sweden. At this follow-up, 44 of the patients included had developed prostate cancer. Men with prostate cancer diagnosis had a higher systolic (P<0.001) and diastolic blood pressure (P<0.000), were more obese as measured by BMI (P=0.010), waist (P=0.007) and hip measurements (P=0.041) than men who did not have prostate cancer diagnosis at follow-up. These men also had a higher uric acid level (P=0.040), and a higher fasting serum insulin level (P=0.023) than men who did not have prostate cancer diagnosis at follow-up. Following exclusion of T1a/b prostate cancer cases, the difference of the fasting serum insulin level between the groups was still significant (P=0.038). Our data support the hypothesis that a higher insulin level is a promoter of prostate cancer. Moreover, our data suggest that the insulin level could be used as a marker of the risk of developing prostate cancer. The present findings also seem to confirm that prostate cancer is a component of the metabolic syndrome. Finally, our data generate the hypothesis that the metabolic syndrome conceals early prostate cancer.