Does finasteride (5-alpha-reductase inhibitor) cause diabetes?

Does Finasteride Cause Diabetes?

Based on the available evidence, there is no conclusive data showing that finasteride directly causes diabetes. While some theoretical concerns exist regarding metabolic effects, the highest quality clinical guidelines do not list diabetes as a known adverse effect of finasteride treatment 1, 2.

Evidence on Finasteride and Metabolic Effects

What We Know:

• The American Society of Clinical Oncology/American Urological Association guidelines thoroughly document finasteride's adverse effects, which primarily include sexual dysfunction (erectile dysfunction, decreased libido), decreased ejaculate volume, and gynecomastia 1.
• These sexual side effects occur in approximately 2-4% more patients taking finasteride compared to placebo 1.
• The most recent and comprehensive clinical guidelines on finasteride use do not mention diabetes as a recognized adverse effect 1, 2.

Emerging Research:

• Some limited research suggests finasteride might have mild effects on metabolic parameters:

  • A small study (n=12) of men treated with 1mg finasteride for androgenetic alopecia showed a significant decrease in glycated hemoglobin (HbA1c) and borderline decrease in insulin resistance after 12 months of treatment 3.
  • This suggests finasteride might actually have a slight beneficial effect on glucose metabolism rather than causing diabetes 3.

• Theoretical concerns have been raised in some research:

  • A 2020 review article hypothesized that long-term 5α-reductase inhibition might contribute to insulin resistance and type 2 diabetes 4.
  • However, this remains theoretical and is not supported by large clinical trials or major guidelines.

Clinical Implications

Monitoring Recommendations:

• Current clinical guidelines do not recommend routine monitoring of glucose levels specifically due to finasteride use 1, 2.
• The primary monitoring recommendations for finasteride focus on:
  • PSA levels (finasteride reduces PSA by approximately 50% after 12 months) 1
  • Sexual function 1
  • Prostate symptom improvement when used for BPH 2

Risk-Benefit Assessment:

• When prescribing finasteride, clinicians should consider:
  • The well-documented adverse effects (primarily sexual dysfunction)
  • The patient's baseline risk factors for metabolic disorders
  • The lack of strong evidence linking finasteride to diabetes development

Conclusion

The current high-quality clinical evidence does not support a causal relationship between finasteride and diabetes. While theoretical concerns exist based on the drug's mechanism of action, the most authoritative clinical guidelines do not list diabetes as a recognized adverse effect of finasteride treatment. The limited research on metabolic effects of finasteride shows mixed results, with some studies even suggesting potential improvements in glucose metabolism parameters.

For patients with existing diabetes or metabolic concerns, standard monitoring of glucose levels would be appropriate as part of routine care, but there is insufficient evidence to suggest that finasteride treatment specifically increases diabetes risk.