SF1 and Infertility: These authors concluded that aromatase seems to be a physiological target of Dax-1 (an orphan nuclear receptor that represses transcription by steroidogenic factor-1, SF-1) in Leydig cells, and increased Cyp19 expression may account, in part, for infertility and Leydig cell hyperplasia (LCH) in Dax1-deficient mice.