Body composition, abdominal fat distribution, and prostate-specific antigen test results

Area of Science:

• Urology
• Endocrinology
• Biostatistics

Background:

• Competing theories explain the inverse association between obesity and prostate-specific antigen (PSA) levels.
• These include endocrine disturbances affecting PSA production and plasma volume dilution of PSA.
• The endocrine theory predicts inverse associations with fat mass and abdominal fat distribution, while plasma volume dilution theory predicts inverse associations with both lean and fat mass, independent of distribution.

Purpose of the Study:

• To investigate the relationship between body composition (fat mass, lean mass, waist circumference) and screening prostate-specific antigen (PSA) levels.
• To determine whether findings support the endocrine disturbance or plasma volume dilution theory.

Main Methods:

• Analysis of data from approximately 8,000 men undergoing routine PSA screening.
• Multivariate linear regression models controlling for age and race/ethnicity were used.
• Evaluated associations between weight, percent body fat, and waist circumference with PSA levels.

Main Results:

• PSA levels showed a significant inverse association with both lean mass and fat mass.
• A 5-pound difference in lean mass was associated with a -0.9% difference in PSA, and fat mass with a -0.7% difference.
• Increased waist circumference was associated with higher PSA levels (+0.9% per inch).

Conclusions:

• Study findings are more consistent with the plasma volume dilution theory.
• The results suggest that increased plasma volume in obese individuals dilutes PSA levels.
• This provides evidence against the endocrine disturbance theory as the primary explanation.