Prostate specific antigen is metabolized in the liver

Purpose: The site of metabolism of prostate specific antigen (PSA) was determined. Materials and Methods: In a prospective study, during clinically indicated left and right heart catheterizations for various cardiac diseases in 12 men (mean age 62.5 +/- 8.3 years, standard deviation), selective blood samples were obtained from the infra-renal, infra-hepatic and suprahepatic inferior vena cava, renal vein, superior vena cava, pulmonary artery and femoral artery. Mean PSA concentration was calculated for all vascular sites. Using a paired Student t test, the mean difference between the afferent and efferent PSA concentrations across the renal, hepatic, pulmonary and pelvic circulation was calculated. Results: The hepatic gradient between the infra-hepatic and suprahepatic inferior vena cava showed the greatest decrease (0.11 +/- 0.16 ng/ml. or 8.3%) in PSA concentration and was statistically significant (p = 0.04). A smaller decrease across the pulmonary circulation was statistically insignificant. No decrease in the PSA concentration was noted across the renal circulation. The PSA concentration increased significantly (0.19 +/- 0.18 ng./ml. or 16.3%, p = 0.003) across the pelvic circulation, confirming the release of PSA from the prostate. Conclusions: PSA is released from the prostate. The kidneys and lungs do not have a significant role in elimination of PSA, and the liver appears to be the most likely site of its metabolism. Although our sample size is small and the PSA range is narrow, our results strongly support these conclusions.