The illusion of prostate-specific antigen decline in patients with metabolic syndrome and insulin resistance

Abstract

Study Type-Symptom prevalence (prospective cohort) Level of Evidence 1b What's known on the subject? and What does the study add? Studies have shown that PSA is negatively associated with obesity as a result of hemodilution or metabolic effect. Hemodilution could be the main reason for low PSA levels in obese men. However, the intrinsic metabolic effects such as insulin resistance (IR) or metabolic syndrome (MS) on PSA level have not been clearly evaluated although obesity is closely tied to MS and IR. We regarded MS and IR as the pathophysiological cornerstone of metabolic disorder in obesity and analyzed the relationships among MS, IR, and PSA levels, and plasma volume by using the concept of PSA mass, the total circulating PSA protein. PSA mass did not change depending on the severity of the obesity, MS or IR. Even the group with both MS and IR, which could be the most metabolically disturbed in this study, did not have different PSA mass, comparing with the group without any MS or IR. Thus, the decline in PSA level in men with MS or IR can be also explained by increased plasma volume other than any intrinsic metabolic effects. Objective: To investigate the detailed mechanism of prostate-specific antigen (PSA) decline in metabolic syndrome (MS) and insulin resistance (IR), which lowers the predictive value of the PSA test, we examined the effect of haemodilution and the possibility of an intrinsic metabolic effect. Patients and Methods: We analysed 28.315 men who underwent routine checkups. We compared the ageadjusted mean PSA levels in subjects with and without MS before and after adjusting or stratifying the plasma volume. We analysed changes in PSA level, plasma volume and PSA mass according to obesity grade, number of MS components, IR severity and diagnosis of MS, IR or both using an analysis of covariance. Results: The PSA levels were lower in the group with MS than in the group without MS (P = 0.001), but this difference disappeared after adjusting or stratifying the plasma volume (P > 0.05 for all). The PSA levels decreased, plasma volume increased, and PSA mass did not change as the number of MS components increased

Prostate‐specific antigen lowering effect of metabolic syndrome is influenced by prostate volume

“…However, most of the previous studies that examined the relationship of MS and PSA did not adjust prostate volume. [1][2][3][4][5][6] Interestingly, the PSA of men with MS was not higher than that without MS in those studies. [1][2][3][4][5][6] Another factor that influences serum PSA level in men with MS is plasma volume.…”

“…[1][2][3][4][5][6] Interestingly, the PSA of men with MS was not higher than that without MS in those studies. [1][2][3][4][5][6] Another factor that influences serum PSA level in men with MS is plasma volume. Men with MS reportedly have a larger plasma volume than men without MS. 6 In the study, PSA mass (serum PSA 9 plasma volume) was used to adjust the plasma volume, and there were no significant differences of PSA mass between men with MS and without MS.…”

“…In contrast, some studies reported that serum PSA level is not influenced by MS. 5,6 A previous study using routine check-up data reported that the serum PSA level of MS patients was slightly lower than of non-MS men (1.119 ng/ mL vs 1.081 ng/mL, P = 0.001), but after adjustment of age and large plasma volume of men with MS, the difference disappeared (1.113 ng/mL vs 1.093 ng/mL, P = 0.10). 5 From this finding, the authors opined that slightly low PSA in men with MS results from hemodilution. Another study also reported that the mean PSA level in men with MS was lower than that in men without MS, although MS was not associated with PSA level after adjustment for age and BMI.…”

“…To modify the influence of plasma volume and prostate volume, PSA mass density was calculated using the following formulae: BSA (m 2 ) = bodyweight (kg) 0.425 9 height (m) 0.725 9 0.007184 Plasma volume (L) = BSA (m 2 ) 9 1.670 PSA mass (lg) = PSA (ng/mL) 9 plasma volume (L) PSA mass density (lg/mL) = PSA mass (lg) / prostate volume (mL) This method of PSA mass calculation is identical with a previous study that reported that low PSA in MS patients could be explained by a hemodilution effect. 5 PSA mass density was developed to adjust the influence of prostate volume.…”

“…It is controversial whether MS influences PSA. Several studies reported that the serum PSA level of men with MS is lower than that of men without MS. [1][2][3][4] In contrast, a few studies reported that serum PSA level was not influenced by MS. 5,6 Furthermore, a report cited that serum PSA level is higher in patients with MS than in patients without MS. 7 These heterogeneous results might be because serum PSA level is influenced by various factors besides the presence of MS. [8][9][10][11][12][13][14] In particular, prostate volume is a well-known factor that is directly proportional to serum PSA level. [9][10][11][12] Therefore, prostate volume should be considered thoroughly to evaluate an influence of MS on PSA, because men with MS have a larger prostate volume than men without MS. [15][16][17][18][19][20][21] Considering higher prostate volume arithmetically, the PSA of patients with MS should be higher than that of patients without MS.…”