KLK3 and obesity due to melanocortin 4 receptor deficiency: Interestingly, the inverse U-shaped association of BMI with PCa risk, as observed in our and other studies6,30, is consistent with the association of BMI with PSA testing activity; normal to overweight men undergo PSA testing the most, while both men with underweight and obesity are screened less, thereby delaying or avoiding a PCa diagnosis7,33.