Secretion of testosterone and its delta4 precursor steroids into spermatic vein blood in men with varicocele-associated infertility.

Insight into the mechanisms by which steroid hormones are released from the testes was sought by examining the concentrations of progesterone, 17alpha-hydroxyprogesterone, and androstenedione as well as testosterone in spermatic vein blood every 15 min for 4 h in men with varicocele-associated infertility. Coincident discrete secretory episodes of all four steroids were found, and spermatic vein concentrations of testosterone were highly positively correlated to the concentrations of progesterone (r = 0.79), 17alpha-hydroxyprogesterone (r = 0.81), and androstenedione (r = 0.82), respectively. The sum of the four measured steroids per mL plasma was calculated, and testosterone was found to account for 70%, 17alpha-hydroxyprogesterone for 24%, androstenedione for 5%, and progesterone for 1% of the total. In a previous study of the intratesticular steroids in a separate population of men with varicocele-associated infertility, the sum of these four steroids per g tissue was similarly calculated. Testosterone accounted for 70% of the four measured steroids, 17alpha-hydroxyprogesterone for 22%, androstenedione for 4%, and progesterone for 3% of the total. Thus, the relative concentrations of these four steroids are nearly identical in testicular tissue and spermatic vein plasma. From these data we hypothesize that steroids in the testicular interstitium are cosecreted into peripheral plasma in response to stimulation by LH and propose that the mechanism initiating this pulsatile mode of secretion oftestosterone and its precursor steroids may not be coupled to testosterone biosynthesis.