The associations between the risk of testicular cancer and other questionnaire-based indicators of infertility (e.g. difficulty impregnating a partner or reported diagnosis of infertility) and clinical measures of infertility (e.g. sperm count and motility, serum Inhibin B, FSH, and testosterone) are less consistent and more difficult to investigate than the number of children fathered, due to problems of reverse causation, measurement errors, and recall and detection bias. This evidence concerns the gene BRD2 and Infertility.