TH and Familial prostate cancer: Previous studies have shown that TH contributes to the regulation of BPH and prostate cancer,[6] and that circulating levels of TH determine the size of the prostate.[14] Another study of T3 as a biomarker of prostate disorders indicated that men with BPH or prostate cancer have significantly elevated serum T3 levels.[15] However, T3 showed no effects on normal human prostate cells, or in vitro on TH receptors expressed in a human prostatic epithelium cell line.[16] In another study, the association between prostate size and TH content was assessed.