A study of androgen biosynthesis by the human testis in vitro

The biosynthetic pathways in human testicular tissue have been studied extensively in our laboratory without the use of radioisotopes. Experiments were conducted with normal testicular tissue from patients undergoing orchiectomy for prostatic cancer. These studies have shown that the preferred pathway of testosterone biosynthesis is influenced by the nature and concentration of cofactor added to the incubation medium. Four enzymes are involved in the transformation of pregnenolone to testosterone, that is, 3 beta-hydroxysteroid dehydrogenase, 17 alpha-hydroxylase, C17-C20 lyase and 17 beta-hydroxysteroid oxidoreductase. Our studies show that the 4-ene pathway predominates in the biosynthesis of testosterone from pregnenolone. Analysis of several samples of human testicular vein blood supports the contention that 4-androsten-3,17-dione is the immediate precursor of testosterone.