Background: In recent years the use of Prostate Specific Antigen test (PSA) has reduced the mortality rate of prostate cancer. Certain factors by affecting the levels of PSA, decrease or increase prostate cancer detection. Some studies suggest the effect of body weight and Body Mass Index (BMI) on PSA, while some others are contrary to the opinion mentioned.. Hence, in this study we examined the relationship between BMI and PSA.

Methods: In the present study 140 patients with LUTS (Lower Urinary Tract Symptoms) that had referred to the Urology clinic of Imam Reza Hospital (affiliated to Mashhad University of Medical Sciences), were studied. Patients with prostate cancer, prostatitis, recurrent UTI, taking finasteride and history of prostate surgery were excluded. The data of body weight, BMI, prostate volume, PSA and Free PSA were collected. Patients were divided in two groups group A with a BMI less than 27 and group B with BMI equal and greater than 27. The data were analyzed with T-test, Correlation and SPSS (version 15).

Results: Mean of age in patients was 63.6 ±9.98.Two groups in regard to age, prostate volume, and Free PSA did not differ statistically. Mean PSA level in group A was 3.9±4.3 and in group B is 2.7±1.3. There is a significant difference in mean PSA level between two groups (p=0.04). We tested the correlation between PSA levels and BMI which were inversely correlated with increased BMI (p=0.04, R=-0.175).

Conclusions: This study showed that PSA is reduced with increasing BMI. However BMI does not affect Free PSA, thus the ratio between total PSA and free PSA rises, delaying prostate cancer diagnosis. The result of the present study showed that in different BMI levels physicians need different PSA cut points to decide on performing prostate biopsy.