Obesity Affects Prostate Cancer Test Results

Elevated levels of prostate specific antigen (PSA) in the blood can be an indicator of prostate cancer and lead to further diagnostic investigations.

Obese men have lower serum prostate-specific antigen (PSA) than comparably aged lean men, but the underlying mechanism remains unclear. A recent study determined the effect of obesity on PSA and the potential contributing mechanisms.


Scientists at the University of Adelaide (Adelaide, Australia) and their colleagues recruited a cohort of 1,195 men aged 35 years and over, with demographic, anthropometric (body mass index (BMI), waist circumference (WC) and serum hormone (serum testosterone (T), estradiol (E2), PSA and hematology assessments obtained over two waves was assessed. Men with a history of prostate cancer or missing PSA were excluded, leaving 970 men for the final analysis. Mixed-effects regressions and mediation analyses adjusting for hormonal and volumetric factors explore the potential mechanisms relating obesity to PSA.

The scientists reported that after adjusting for age, PSA levels were lower in men with greater WC. In a multivariable model including WC, age, E2/T and PlasV as predictors, no statistically significant associations were observed between with PSA and either WC or PlasV, while strong associations were observed with both E2/T and age. In the mediation analyses with PlasV as the mediator, the average causal mediation effect (ACME) explained roughly 0.2 of the total effect of WC on PSA, while when E2/T is a mediator; the ACME explained roughly 0.5 of the effect.

The authors concluded that their findings indicate that lower PSA levels in obese men, as compared to normal weight men, can be explained both by hormonal changes (elevated E2/T ratio) and haemodilution. Hormonal factors therefore represent a substantial but underappreciated mediating pathway.

Adel Aref, MBBch, MSc, a Clinical Oncologist, and first author of the study, said, “PSA is increased by the male sex steroid hormone, testosterone. We have shown for the first time that the concentration of PSA in the blood is lower in men with severe obesity (with a body mass index or BMI of 30 or higher) than in lean men, and that this can be attributed to lower concentrations of circulating testosterone.” The study was published on June 25, 2018, in the journal Endocrine-Related Cancer.

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