What dihydrotestosterone (DHT) level is associated with androgenetic alopecia in adult males using exogenous testosterone?

DHT Levels and Hair Loss in Men Using Exogenous Testosterone

There is no specific DHT threshold that predicts androgenetic alopecia in men using exogenous testosterone—hair loss depends on genetically-determined follicular sensitivity to DHT rather than absolute serum DHT levels.

The Critical Distinction: Sensitivity vs. Absolute Levels

The relationship between DHT and hair loss is fundamentally about tissue sensitivity, not serum concentration. Research demonstrates that:

• Serum DHT levels do not correlate with the severity or presence of androgenetic alopecia 1
• Men with androgenetic alopecia show increased serum DHT and free testosterone compared to controls, but these elevations do not predict which individuals will experience hair loss 2
• The genetically-determined sensitivity of hair follicles to DHT is the primary determinant of hair loss, not the circulating DHT concentration 1

What Happens to DHT with Exogenous Testosterone

When men use exogenous testosterone replacement therapy:

• Testosterone levels increase by approximately 10% above baseline 3
• DHT is produced locally in scalp tissue through conversion of testosterone by 5-alpha-reductase type 2 4
• The amount of DHT produced depends on local enzyme activity in the scalp, not just serum testosterone levels 4

Importantly, testosterone replacement therapy does not require monitoring of DHT levels, as the guidelines focus on monitoring testosterone levels (targeting 500-600 ng/dL midway between injections), hematocrit, and PSA—not DHT 5

Why Measuring DHT Doesn't Help Predict Hair Loss

Multiple lines of evidence demonstrate the futility of using DHT measurements:

• A study of 49 patients with androgenetic alopecia found increased serum DHT in most patients (17 of 19 women, 5 of 9 men), but also found elevated DHT in healthy controls without hair loss 1
• Mean DHT values showed no significant differences between patients with alopecia and controls 1
• Increased serum DHT concentrations did not correlate with the advancement or severity of alopecia 1

The Mechanism That Actually Matters

Androgenetic alopecia occurs through:

• Local scalp tissue DHT production: Scalp skin DHT levels are what drive follicular miniaturization, not serum DHT 4
• Genetic follicular sensitivity: Hair follicles in genetically susceptible individuals respond to normal or even low-normal DHT levels by miniaturizing 1
• Variable enzyme expression: The amount of 5-alpha-reductase type 2 in scalp tissue varies between individuals, creating different local DHT concentrations regardless of serum levels 4

Clinical Implications for Men on Testosterone Therapy

If hair loss occurs during testosterone replacement therapy:

• The hair loss is due to genetic predisposition to androgenetic alopecia being unmasked or accelerated by testosterone therapy 6
• Measuring serum DHT will not provide actionable information, as the problem is follicular sensitivity, not DHT levels 1
• Treatment options include finasteride (which reduces scalp DHT by 64-69% at 1-5 mg daily doses) or minoxidil, both of which are superior to placebo for promoting hair growth 4, 6

Treatment Considerations

For men experiencing hair loss while on testosterone therapy:

• Finasteride 1 mg daily reduces serum DHT by approximately 70% and increases hair density in 48% of men after one year and 66% after two years 3, 6
• Finasteride doses as low as 0.2 mg daily maximally decrease both scalp skin and serum DHT levels 4
• Patients with lower post-treatment DHT and free testosterone levels show higher rates of improvement in hair loss severity 2
• Critical caveat: Finasteride is absolutely contraindicated in men seeking fertility preservation, as it may affect reproductive function 5

The Bottom Line

Do not measure DHT levels to predict or diagnose hair loss in men using exogenous testosterone. The decision to treat hair loss should be based on clinical observation of hair thinning, not laboratory values. If treatment is desired, finasteride or minoxidil are evidence-based options, but the choice to treat hair loss versus continuing testosterone therapy depends on the patient's priorities regarding sexual function (which improves with testosterone) versus cosmetic concerns 5, 6.