Genetically elevated bioavailable testosterone level was associated with the occurrence of benign prostatic hyperplasia.

backgroundRecent studies identified several risk factors of benign prostatic hyperplasia (BPH), including dyslipidemia, type 2 diabetes mellitus, hypertension, and obesity. But they were not so reliable and some studies contradicted with one another. Hence, a reliable method is urgently needed to explore exact factors that facilitated BPH development.

methodsThe study was based on Mendelian randomization (MR) design. All participants were from the most recent genome-wide association studies (GWAS) with large sample size. The causal associations between nine phenotypes (total testosterone level, bioavailable testosterone level, sex hormone-binding globulin, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, type 2 diabetes mellitus, hyper-tension, and body mass index) and BPH outcome were estimated. Two sample MR, bidirectional MR, and multivariate MR (MVMR) were performed.

resultsIncrease in bioavailable testosterone level was able to induce BPH based on nearly all combination methods [beta (95% confidence interval (CI)): 0.20 (0.06-0.34) for inverse variance weighted (IVW)]. The other traits seemed to interact with testosterone level and did not cause BPH generally. Higher triglycerides level was likely to raise bioavailable testosterone level [beta (95% CI): 0.04 (0.01-0.06) for IVW]. In MVMR model, bioavailable testosterone level was still associated with BPH occurrence [beta (95% CI) 0.27 (0.03-0.50) for IVW].

conclusionsWe for the first time validated the central role of bioavailable testosterone level in the pathogenesis of BPH. The complex associations between other traits and BPH should be further investigated.