What are the treatment options for hair loss caused by Dihydrotestosterone (DHT)?

DHT and Hair Loss Treatment

First-Line Treatment for Androgenetic Alopecia

For DHT-related male pattern hair loss (androgenetic alopecia), finasteride 1 mg daily is the definitive treatment, blocking the conversion of testosterone to DHT and demonstrating proven efficacy in slowing hair loss and promoting regrowth. 1, 2

Mechanism and Rationale

• DHT is the primary culprit: Dihydrotestosterone (DHT) causes miniaturization of hair follicles by binding to androgen receptors, shortening the anagen (growth) phase and prolonging the telogen (resting) phase, leading to progressive hair loss 3

• Finasteride blocks DHT production: As a competitive inhibitor of Type II 5α-reductase, finasteride prevents the conversion of testosterone to DHT, reducing serum DHT by approximately 70% and scalp DHT by 64-69% at the 1 mg dose 1, 4

• Testosterone levels remain normal: While DHT decreases dramatically, circulating testosterone increases by only 10-15%, remaining within physiologic range, with no clinically meaningful effects on the hypothalamic-pituitary-testicular axis 1

Clinical Efficacy Data

• Proven hair regrowth: In clinical trials of 1,553 men with male pattern hair loss, finasteride 1 mg daily produced clinically significant increases in hair count of 107 hairs at 1 year and 138 hairs at 2 years (measured in a 5.1 cm² area of balding vertex scalp) compared to progressive hair loss with placebo 2

• Sustained improvement: Global photographs showed improvement in 48% of finasteride recipients at 1 year and 66% at 2 years, compared to only 7% of placebo recipients at both time points 5, 2

• Prevention of further loss: 83% of finasteride-treated men had no further hair loss compared to baseline after 2 years, versus only 28% of placebo recipients 5

Dosing and Onset of Action

• Standard dose: 1 mg orally once daily is the established dose for male pattern hair loss 1, 2

• Dose-response relationship: Doses as low as 0.2 mg daily maximally decrease both scalp skin and serum DHT levels, though 1 mg is the clinically validated dose 4

• Timeline for results: Maximum DHT suppression occurs within 8 hours of the first dose and is maintained throughout the 24-hour dosing interval; however, visible hair regrowth typically requires 3-12 months of continuous treatment 1, 2

Safety Profile and Side Effects

• Generally well-tolerated: In phase III studies, only 3.8% of finasteride recipients versus 2.1% of placebo recipients reported sexual function disorders (decreased libido, ejaculation disorder, erectile dysfunction) 5

• Reversible adverse effects: All sexual adverse events reversed upon discontinuation of therapy, and many resolved even with continued treatment 5

• PSA monitoring consideration: Finasteride reduces serum PSA by approximately 50% after 1 year; when screening for prostate cancer, the measured PSA value should be doubled to accurately gauge disease progression 6

Absolute Contraindications

• Pregnancy: Finasteride is absolutely contraindicated in pregnant women due to risk of hypospadias in male fetuses; women of childbearing potential should not handle crushed or broken tablets 5

• Women generally: Finasteride is not indicated for female pattern hair loss 1

Alternative and Adjunctive Options

• Topical minoxidil: Can be used alone or in combination with finasteride; animal studies suggest an additive effect when combined, though head-to-head comparisons in humans are lacking 5, 7

• Dutasteride: Inhibits both Type I and Type II 5α-reductase (versus finasteride's Type II only), reducing serum DHT by 95% versus 70% with finasteride, though it is not FDA-approved for hair loss 6

Common Pitfalls to Avoid

• Premature discontinuation: Patients must understand that visible improvement requires months of continuous treatment, and discontinuation results in return of DHT levels to pretreatment values within approximately 2 weeks 1

• Expecting immediate results: Hair regrowth cannot be expected within 3 months; setting realistic expectations is critical for treatment adherence 8

• Ignoring the distinction from alopecia areata: The evidence provided includes extensive discussion of alopecia areata (an autoimmune condition), which is entirely different from androgenetic alopecia and requires different treatments (intralesional corticosteroids, contact immunotherapy); DHT-related hair loss specifically refers to androgenetic alopecia 6, 8