Testosterone and Some of Its Precursors and Metabolites in the Human Epididymis*

The concentrations of testosterone, four of its precursors (pregnenolone, progesterone, 17 alpha-hydroxyprogesterone, and androstenedione), and three of its metabolites (5 alpha-dihydrotesterone, 5 alpha-androstane-3 alpha, 17 beta-diol, and androsterone) were measured in the epididymis and proximal ductus deferens of elderly men with prostatic carcinoma. In addition, they were measured in testis tissue and spermatic and p eripheral blood sera.l The main androgen in the epididymis was testosterone [37.3 +/- 22.0 (SD) ng/g wet tissue]; 5 alpha-dihydrotestosterone was also present in a relatively high concentration [9.7 +/- 6.5 (SD) ng/g wet tissue]. There were no steroid concentration gradients along the epididymis. The actual and relative concentrations of the steroids measured strongly suggest that they are transferred from testes to epididymides in the testicular lymph or rete testis fluid. Estrogen administration led to significant decreases in epididymal androstenedione, testosterone, and 5 alpha-dihydrotestosterone concentrations. Thus, one facet of the deleterious effects of estrogen on male reproductive functions may be interference with normal epididymal function, essential for undisturbed sperm maturation.