Can finasteride (Propecia) affect metabolism?

Finasteride's Effects on Metabolism

Finasteride can affect metabolism, primarily through its impact on hormone levels, with research showing mild changes in metabolic profile including potential improvements in glucose metabolism regulation after 12 months of treatment. 1

Mechanism of Action and Metabolic Effects

Finasteride works by inhibiting type II 5α-reductase, which converts testosterone to dihydrotestosterone (DHT). This mechanism leads to several metabolic changes:

• Hormonal changes:

  • Decreases DHT levels by approximately 70% with daily dosing 2
  • Increases circulating testosterone by 10-20% (remaining within physiologic range) 2
  • Increases luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by about 10% 2

• Lipid profile effects:

  • Initial increase in total cholesterol, HDL-cholesterol, and LDL-cholesterol that stabilizes with prolonged treatment 1
  • No clinically meaningful effect on overall plasma lipid profile according to FDA data 2

• Glucose metabolism:

  • Significant decrease in glycated hemoglobin (HbA1c) after 12 months of treatment 1
  • Borderline decrease in insulin resistance as measured by rate constant for plasma glucose disappearance (kITT) 1

Dosage Considerations

• The metabolic effects have been observed at both treatment doses:

  • 1 mg/day (used for androgenetic alopecia) 1, 3
  • 5 mg/day (used for benign prostatic hyperplasia) 2, 4

• Doses below 0.5 mg/day produce minimal DHT suppression, while doses above 5 mg/day offer little additional benefit 4

Time Course of Effects

• Single dose produces rapid reduction in serum DHT, with maximum effect observed 8 hours after administration 2
• DHT suppression is maintained throughout the 24-hour dosing interval 2
• Metabolic changes may take longer to manifest, with significant changes in glucose metabolism parameters observed after 12 months of treatment 1

Clinical Implications

• The mild improvement in glucose metabolism regulation suggests finasteride might have a positive effect on metabolic syndrome features often associated with androgenetic alopecia 1
• These metabolic effects appear to be secondary to the hormonal changes induced by finasteride rather than direct effects on metabolism

Monitoring Considerations

• For patients on long-term finasteride therapy, consider:
  • Monitoring lipid profile during the first few months of treatment as initial changes may occur 1
  • Assessing glucose metabolism parameters in patients with pre-existing metabolic issues 1
  • Being aware that PSA levels will decrease with finasteride administration (approximately half of normal range) 4

Conclusion

While finasteride's primary action is on DHT levels for treating androgenetic alopecia or benign prostatic hyperplasia, it does have mild effects on metabolism, particularly regarding glucose regulation. These effects should be considered when prescribing finasteride, especially for patients with pre-existing metabolic conditions.