KLK3 and obesity due to melanocortin 4 receptor deficiency: This possibility has been suggested because digital rectal examination is technically more difficult in obese patients [9], biopsies are more likely to lead to false negative findings due to enlarged tissue [9] and epidemiological studies have found that prostate specific antigen (PSA) concentrations are lower in obese than in non-obese men [12]–[14], possibly due to greater plasma volume in obesity resulting in haemodilution and therefore lower relative concentrations of PSA [15].