Do 5α-Reductase Inhibitors Raise Circulating Serum Testosterone Levels? A Comprehensive Review and Meta-Analysis to Explaining Paradoxical Results.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of clinical studies.
PubMed 30098986 · doi:10.1016/j.sxmr.2018.06.002
What was done
The authors searched PubMed and EMBASE for studies assessing circulating serum testosterone (T) changes in men treated with finasteride or dutasteride. Forty studies were reviewed qualitatively, and 11 studies with 1,784 patients (aged 18–83 years, average follow-up 17 months) were pooled in a random-effects meta-analysis. Changes in LH, FSH, SHBG, and estradiol across 10 studies were also evaluated.
What was found
The meta-analysis of 11 studies showed a mean baseline change in serum testosterone of 27 (95% CI 1–54; units not reported in abstract). The increase was not uniform across studies, and sensitivity analysis indicated no single study decisively drove the outcome. Ten studies assessing LH, FSH, SHBG, and estradiol reported no significant changes in these hormone levels.
Why it matters
This review clarifies that 5α-reductase inhibitors do not reliably or meaningfully increase circulating testosterone levels in clinical practice, countering assumptions that blocking DHT conversion systematically elevates serum testosterone.
Limits
The abstract does not state the measurement units for the testosterone estimate, nor does it specify the underlying design of included studies (e.g., randomized vs. observational). Findings are limited by substantial variability between studies and potential differences across subgroups such as baseline testosterone status.
Cited by
- contradicts Inhibiting the 5-alpha reductase enzyme results in a proportional increase of 15% to 20% in intra-tissue estradiol.