Abstract
PURPOSE: Pathways involving sex hormones and insulin-like growth factors (IGFs) have been proposed to explain, in part, the lower risk of prostate cancer among men with diabetes. To gain insights into potential biological mechanisms we explored differences in serum concentrations of sex hormones and IGFs across the trajectory from normoglycemia to prediabetes to poorly controlled diabetes. METHODS: Using cross-sectional data from the National Health and Nutrition Examination Survey III we examined differences in levels of circulating sex hormones, sex hormone-binding globulin (SHBG), IGF-1, and IFG-binding protein 3 (IGFBP-3), according to diabetes status: no diabetes [n = 648], prediabetes [n = 578], undiagnosed diabetes [n = 106], well-controlled diabetes [n = 42], and poorly controlled diabetes [n = 56]. Adjusted geometric mean concentrations were derived using multivariable linear regression, adjusted for age, race, and other lifestyle factors. RESULTS: Total testosterone concentrations were lower among prediabetics (4.89 ng/mL, 95% confidence interval (CI) 4.95-5.21) than men without prediabetes/diabetes (5.29 ng/mL, 95% CI 5.06-5.53) but did not reduce further across diabetes groups. Concentrations of estradiol, estimated free testosterone, SHGB, IGF-1, and IGFBP-3 did not differ. While the ratio of IGF-1 to IGFBP-3 was lower among men with prediabetics and undiagnosed diabetes than men without prediabetes/diabetes, there was no trend across groups. A positive trend for the ratio of estradiol-to-testosterone levels was observed across groups (p trend = 0.045). CONCLUSION: Our findings do not provide clear support for either an androgen driven or IGF-driven pathway for the inverse association between diabetes and prostate cancer risk.