How can I reduce DHT levels and treat related conditions like androgenetic alopecia and benign prostatic hyperplasia?

Reducing DHT Levels: Medical Management

For benign prostatic hyperplasia (BPH), use 5-alpha reductase inhibitors (5-ARIs) in men with prostate volume >30cc or PSA >1.5 ng/mL; for androgenetic alopecia, finasteride 1 mg daily is the evidence-based treatment. 1, 2

Mechanism of DHT Reduction

5-ARIs work by inhibiting the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT). 1

Two Available Medications:

• Finasteride: Selectively inhibits type II 5-alpha reductase isoenzyme, reducing serum DHT by approximately 70% and prostatic tissue DHT by 80%. 1, 2
• Dutasteride: Inhibits both type I and type II isoenzymes, reducing serum DHT by 95% and prostatic tissue DHT by 94%. 1, 3

Treatment for Benign Prostatic Hyperplasia

Reserve 5-ARIs for men with objectively enlarged prostates (>30cc) or PSA >1.5 ng/mL, as smaller glands will not respond reliably. 1

Expected Outcomes:

• Prostate volume reduction of 15-25% at 6 months 1
• IPSS improvement of 3-4 points maintained for 6-10 years 1
• Reduced risk of acute urinary retention and BPH-related surgery 1
• Clinical progression (defined as IPSS increase ≥4, acute urinary retention, UTI, or BPH surgery) reduced from 36% to 21% with dutasteride 1

Critical Counseling Points:

• Slow onset of action: Symptom improvement takes months, unlike alpha-blockers which work within days. 1
• PSA monitoring: After 1 year of 5-ARI therapy, double the measured PSA value to accurately screen for prostate cancer. 1
• Sexual side effects: Decreased libido, ejaculatory dysfunction, and erectile dysfunction occur, though typically resolve after the first year. 1
• Gynecomastia: Can occur with 5-ARI therapy. 1

Comparative Efficacy:

No clinically significant differences exist between finasteride and dutasteride regarding prostate volume reduction, symptom scores, or urinary flow rates in head-to-head comparison. 1 Despite dutasteride's greater DHT suppression (95% vs 70%), this doesn't translate to superior clinical outcomes because type II 5-alpha reductase predominates in prostatic tissue. 1

Treatment for Androgenetic Alopecia

Finasteride 1 mg daily is the FDA-approved treatment for male pattern hair loss. 2, 4

Expected Outcomes:

• Visible hair growth in up to 66% of men with mild-to-moderate alopecia 5
• Most importantly: Stops hair loss progression in 91% of patients 5
• The preservative effect is critical—finasteride prevents further loss by growing enough hair to maintain scalp coverage 5
• Hair loss resumes upon discontinuation 5

Treatment Strategy:

Prescribe finasteride early in androgenetic alopecia before significant hair loss occurs, as its primary benefit is preservation rather than restoration. 5 The medication works by reducing scalp DHT levels, which drives miniaturization of hair follicles. 4, 6

Adverse Effects:

• Reduced libido, decreased ejaculate volume, and gynecomastia are the most common side effects 4
• Post-finasteride syndrome (PFS)—a controversial constellation of persistent sexual, physical, and psychological symptoms after discontinuation—has been reported but remains poorly defined 1

Important Caveats and Monitoring

Metabolic Considerations:

5-ARIs may contribute to fat accumulation in the liver (potentially predisposing to NAFLD), increased glucose synthesis, reduced glucose disposal, and worsening insulin resistance. 7 These metabolic effects warrant consideration when prescribing for BPH or alopecia. 7

Testosterone Levels:

Circulating testosterone increases by 10-20% with finasteride but remains within physiologic range. 2 This compensatory increase does not cause adverse effects. 2

Perioperative Use:

Consider 5-ARIs preoperatively to reduce intraoperative bleeding and transfusion requirements for TURP or other BPH surgeries. 1

Contraindications:

Finasteride is contraindicated in women of childbearing potential due to teratogenic effects on male fetal development. 2 Pregnant women should not handle crushed or broken tablets. 2

Dosing Specifics

• BPH: Finasteride 5 mg daily or dutasteride 0.5 mg daily 1, 3
• Androgenetic alopecia: Finasteride 1 mg daily 2, 4
• Bioavailability: 63% for finasteride, not affected by food 2
• Time to steady state: Slow accumulation occurs; mean trough concentrations reach 9.4 ng/mL after >1 year in BPH patients 2
• Discontinuation: DHT levels return to baseline approximately 2 weeks after stopping; prostate volume returns to near-baseline after 3 months 2