Influence of continuous luteinizing hormone-releasing hormone agonist treatment on steroidogenic enzymes in the human testis.

Nine elderly men with prostatic carcinoma underwent treatment with a LHRH-agonist (Zoladex, ICI) for 3-6 months. At the end of the treatment period the patients underwent subcapsular orchidectomy. Testicular tissue was incubated with different tritiated testosterone precursors. Conversion mediated by several testicular steroidogenic enzymes was compared between Zoladex-treated patients and nineteen non-treated patients who underwent orchidectomy because of prostatic carcinoma. Serum concentrations of LH, FSH and testosterone were determined before and during treatment in the treated patients. The LHRH agonist treatment induced significantly decreased conversion mediated by the enzymes 3 beta-hydroxysteroid dehydrogenase, 17 alpha-hydroxylase and C17-20 lyase. Conversion mediated by 17 beta-ketosteroid reductase was also decreased although not as dramatically as the other enzymes, while conversion mediated by 20 alpha-dehydrogenase was increased. Serum concentrations of testosterone decreased to castration levels. Serum gonadotrophins decreased but remained within normal levels suggesting that "desensitization" at the pituitary level was not the only mechanism of action of the LHRH-agonist.