KLK3 and prostate cancer: There was a small difference in the proportion of men diagnosed with prostate cancer as a result of a health examination (i.e. PSA-testing) between men that had fathered dizygotic twins (21%) and men that had fathered singletons (22%), (Table 2) likely due to a calendar effect since fathers of dizygotic twins were diagnosed somewhat more often in the pre-PSA era, Table 3.