KLK3 and prostate cancer: An increase in prostate specific antigen (PSA) within the first 12 months of initiating testosterone treatment[13, 14], combined with the association between testosterone treatment and increases in prostate size, raises concerns about the possible increase in prostate cancer risk.[15–18] Testosterone treatment could increase the near-term risk of prostate cancer by stimulating an occult tumor or it may impact risk over a longer period of time.