In vitro-metabolism of 3H-progesterone in human testicular tissue: I Adult males.

: Androgen biosynthesis in the male gonads may be analysed in some detail by means of in vitro incubation of minor testicular biopsy specimens with various radiolabelled steroid precursors. We have investigated nine adult human male voluteers without apparent gonadal dysfunction with regard to their in vitro metabolism of 3H-progesterone. The following metabolic compounds were recovered: 20a-dihydroprogesterone, 17a-hydroxyprogesterone, 20a, 17a-dihydroxyprogesterone, androstenedione and testosterone. No significant amounts of 5a-reduced delta4-3-oxo-steroids or oestrogens were found. The major metabolites formed were 20a-dihydroprogesterone and 17a-hydroxyprogesterone, which accounted for 13-49 per cent and 17-47 per cent, respectively, of all newly synthesized steroid compounds. Radiolabelled delta4-3-oxo-C19-metabolites were recovered in minor amounts only, possibly due to metabolic interference with the endogenous pool of cold mass compounds. The individual steroid metabolic patterns were found to be poorly related to the individual levels of FSH, ICSH (LH) and testosterone in the peripheral circulation. Adequate knowledge of the steroid metabolic pathways generally utilized in ordinary testicular tissue in vitro is a prerequisite for the evaluation of steroid metabolism in males with various types of gonadal dysfunction.