Secretion by the human testis of epitestosterone, with its sulfoconjugate and precursor androgen 5-androstene-3 beta,17 alpha-diol.

Epitestosterone (ET) and testosterone (T), free and sulfoconjugated, as well as 5-androstene-3 beta,17 alpha-diol (5AD3 beta 17 alpha) and its 17 beta-epimer have been analyzed, by gas chromatography-mass spectrometry with stable isotope dilution, in peripheral and spermatic venous plasma of patients with left varicocele. All these androgens are secreted by the testis as evidenced by the significant concentration gradients between peripheral and spermatic venous plasma. Half of the daily ET production is ascribed to the testis, while 95% of T sulfate and roughly 70% of ET sulfate are also of testicular origin. Significant correlations between ET and 5AD3 beta 17 alpha are an indication that the 5-ene pathway is also operative for ET biosynthesis. High ratios of spermatic to peripheral venous plasma levels of ET and 5AD3 beta 17 alpha are also related to the high clearance rates of 17 alpha-hydroxy-androgens.