In present study, our results demonstrated that PV was positively associated with serum PSA concentrations, but BMI and BV inversely related to PSA levels, indicating BMI, BV and PV should be taken into account when referring men to a prostate biopsy based on serum PSA concentrations. Furthermore, this present study demonstrated that a higher BMI might have a higher PV and BV. In addition, we introduced new serum PSA-related parameters (PSA density and PSA mass) to associate with BMI in different categories, demonstrated that PSA mass was not related to BMI in Chinese general men.
Our results showed that serum PSA concentrations decreased with increasing BMI among Chinese general men with no previous prostate cancer diagnosis. This confirms results from earlier studies showing inverse associations between BMI and serum PSA [13, 14, 12, 5–8]. Obesity plays a key role in developing abnormalities in sex hormone metabolism and insulin levels, as the excess accumulation of adipose tissue or body fat. It can lead to benign prostatic enlargement by raising estrogen and estradiol levels, while lowering testosterone and serum globulin binding protein levels . The elevated estrogen/testosterone ratio associated with obesity might increase the stromal/epithelial cell ratio in benign prostatic hyperplasianodules .
Previous studies presented that higher BMI might have larger BV [8, 12], which could bias real PSA serum concentrations, and this findings were confirmed in present study. The theory behind the hypothesis is that the same total amount of PSA released from cells in the prostate should be diluted into lower concentrations in men with larger as opposed to smaller BV. Moreover, we found that the BMI was positively correlated with PV and the PV was positively correlated with the level of PSA. However, the BMI was negatively correlated with PSA level. One explanation is following: on the one hand, higher BMI might cause larger PV, and then increase PSA levels. On the other hand, higher BMI could cause hemodilution because the BV has increased, and the hemodilution effect of blood volume on PSA was greater than the increasing effect of PV on PSA [8, 17]. Our results also supported the hypothesis.
Based on the impact of BV and PV on PSA levels, it is necessary to make a comprehensive judgment by combining BV and PV. Some new PSA parameters had been proposed to eliminate the effects of these factors on PSA and improve the sensitivity and specificity of prostate cancer screening. We separately estimated PSA density and PSA mass as PSA concentration divided by PV and PSA concentration times BV, showed that PSA density concentration showed an inverse correlation with BMI, but PSA mass showed no significant correlation to BMI. Our analysis results indicated that using PSA mass to assess PSA concentration will not be affected by obesity in Chinese general men.
There were some limitations in our study, such as being a cross section study. Second, because the study participants were Chinese, the data may not necessarily represent populations outside China. Moreover, our study did not do other analysis of other obesity indices apart from BMI. In addition, we did not investigate the socioeconomic factors and other potential confounders which might influence the BMI and PSA levels. However, our findings are consistent with those of numerous studies conducted in other regions.