Finasteride, an inhibitor of 5 α-reductase, suppresses prostatic dihydrotestosterone in men with benign prostatic hyperplasia

John D. McConnell, Jean D. Wilson, Fredrick W. George, Jack Geller, Fran Pappas, Elizabeth Stoner

Research output: Contribution to journalArticlepeer-review

306 Scopus citations


The oral administration of finasteride, a 4-aza-steroid inhibitor of 5 α-reductase, decreases serum dihydrotestosterone levels, but has little effect on serum testosterone. The current study was designed to assess the effect of finasteride on dihydrotestosterone levels in the prostates of men with benign prostatic hyperplasia. In a double blind, placebo-controlled study, 69 men with symptomatic prostatic hyperplasia were treated with placebo or 5, 10, 50, or 100 mg/day finasteride for 7 days before transurethral resection of the prostate. In the placebo group the mean concentration of prostatic dihydrotestosterone was 10.3 ± 0.6 nmol/kg (± SE), and the mean concentration of testosterone was 0.7 ± 0.1 nmol/kg. After 7 days of treatment with all doses of finasteride, prostatic dihydrotestosterone declined to 15% or less of control levels, and the testosterone concentration increased in a reciprocal fashion. Compared to the placebo group, there was no significant difference in the mean prostatic dihydrotestosterone level achieved in any of the finasteride-treated groups. However, prostatic dihydrotestosterone levels were lower in the groups receiving higher doses of the drug. In two additional patients, finasteride treatment for 2 days also caused a decrease in prostatic dihydrotestosterone levels. No significant adverse experiences occurred during the study. We conclude that finasteride causes profound decrease in prostatic dihydrotestosterone.

Original languageEnglish (US)
Pages (from-to)505-508
Number of pages4
JournalJournal of Clinical Endocrinology and Metabolism
Issue number3
StatePublished - Mar 1992

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical


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