Background: Diabetes mellitus (DM) has been associated with decreased risk of prostate cancer (PC) in several reports. Hormonal environment of diabetic patients is believed to be an important contributing factor in this regard.
Methods: Using data from a multi-center case-control study in Iran, base line testosterone, sex hormone binding globulin (SHBG), estradiol, and albumin levels as well as thorough demographic and medical characteristics of 194 newly diagnosed prostate cancer patients were determined. There were 317 ethnicity-matched men with no cancer as controls as well. Data was analyzed for hormones of interest in DM patients regarding their cancer status.
Results: Of 511 enrolled patients, twenty-one cases and 63 controls were diagnosed as DM. Patients with DM were significantly less likely to have PC (OR: 0.44, P = 0.003). Time since DM diagnosis was also inversely correlated with the risk of cancer (P trend < 0.0001). Control patients had significantly higher testosterone, estradiol, and testosterone/SHBG ratio (P < 0.05). As time since DM diagnosis increased by quartiles, testosterone significantly increased (P trend < 0.05). The risk of PC also significantly declined (P trend < 0.0001) following an initial remarkable increase early after DM diagnosis. After including the hormones in the logistic regression model, there was a weak, yet significant inverse association of testosterone/SHBG and DM duration with the risk of PC.
Conclusions: Based on our results DM duration is inversely correlated with the risk of prostate cancer. Our results do not support the hypothesis that sex hormones, including testosterone, play a major role in the protective effect of DM against PC.
Copyright 2009 Wiley-Liss, Inc.