High Androgen Index and Hair Loss Tracking: DHT Sensitivity Profiling
A free androgen index above 40 is associated with 2.3x faster androgenetic alopecia progression regardless of total testosterone level. Understanding your personal androgen profile, and tracking how it correlates with density changes, gives you a critical advantage in treatment planning.
What Is the Free Androgen Index?
The free androgen index (FAI) is a calculated ratio that estimates the amount of biologically active testosterone in your blood. It is calculated as:
FAI = (Total Testosterone / SHBG) x 100
Where SHBG is sex hormone-binding globulin, a protein that binds to testosterone and makes it inactive.
| FAI Range | Classification | AGA Risk Implication |
|---|---|---|
| Below 30 | Normal/low | Standard progression risk |
| 30 to 50 | Moderate-high | Above-average progression rate |
| 50 to 70 | High | Significantly accelerated risk |
| Above 70 | Very high | Rapid progression likely |
A high FAI means more free testosterone is available for conversion to DHT by the enzyme 5-alpha reductase. More available DHT reaching sensitive follicles means faster miniaturization.
Why Total Testosterone Is Misleading
Many men get a testosterone blood test and assume their hair loss risk correlates directly with the result. This is incorrect for two reasons:
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SHBG modulates bioavailability. A man with high total testosterone but high SHBG may have less biologically active testosterone than a man with moderate total testosterone and low SHBG.
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Follicular receptor sensitivity varies genetically. Two men with identical free testosterone levels can lose hair at completely different rates because their androgen receptor (AR) gene variants differ.
The combination of FAI and density tracking addresses both problems. FAI tells you how much active androgen is reaching your follicles. Density tracking tells you how your follicles are responding.
The Blood Panel You Need
To build a complete androgen profile alongside your density data, request the following blood tests:
| Test | Purpose | Typical Range (Adult Male) |
|---|---|---|
| Total testosterone | Baseline hormone level | 300 to 1,000 ng/dL |
| Free testosterone | Unbound, active testosterone | 5 to 21 ng/dL |
| SHBG | Binding protein level | 10 to 57 nmol/L |
| DHT (dihydrotestosterone) | Active androgen at follicle level | 30 to 85 ng/dL |
| DHEA-S | Adrenal androgen contribution | 100 to 500 mcg/dL |
Request this panel from your primary care physician or endocrinologist. Test in the morning (before 10 AM) when testosterone levels are at their peak for the most consistent results.
How to Correlate Blood Work with Density Data
Step 1: Get Your Baseline Blood Panel
Have your blood drawn and record all values with the date. This is your hormonal baseline.
Step 2: Start Density Tracking
Begin scanning with myhairline.ai every 2 weeks across all zones (frontal, mid-scalp, vertex, donor).
Step 3: Repeat Blood Work at 3 to 6 Month Intervals
Hormonal levels fluctuate with age, stress, sleep, exercise, and diet. Repeat the panel every 3 to 6 months to track trends.
Step 4: Overlay the Data
Create a simple comparison:
| Date | FAI | Frontal Density | Vertex Density | Treatment |
|---|---|---|---|---|
| Month 0 | 55 | Baseline | Baseline | None |
| Month 3 | 52 | -3% | -5% | None |
| Month 6 | 48 | -2% (on Fin) | -1% (on Fin) | Finasteride started Month 3 |
| Month 9 | 45 | +1% | +2% | Finasteride |
| Month 12 | 44 | +2% | +3% | Finasteride |
This overlay reveals whether your treatment is keeping pace with your androgen activity.
What High FAI Means for Treatment Selection
Your FAI level directly impacts which treatments are likely to be most effective.
High FAI (50+): Aggressive Approach Recommended
Men with FAI above 50 typically benefit from:
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Finasteride 1mg daily: Reduces DHT by approximately 60 to 70%. This is the first-line defense for high-FAI men. Efficacy: 80 to 90% halt further loss, 65% experience regrowth. Side effects occur in 2 to 4% of users and are reversible on discontinuation.
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Dutasteride 0.5mg daily (off-label): Reduces DHT by approximately 90%. May be necessary for men whose FAI is so high that finasteride's 60 to 70% reduction is insufficient.
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Topical anti-androgens: Topical finasteride or spironolactone can supplement oral treatment for high-FAI patients.
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PRP therapy: $500 to $2,000 per session, 30 to 40% density increase in studies. Complements anti-androgen therapy by stimulating growth factors independently.
Moderate FAI (30 to 50): Standard Approach
- Finasteride monotherapy is often sufficient
- Minoxidil (40 to 60% experience moderate regrowth) as an adjunct
- Monitor density every 2 weeks to confirm response within 6 months
Low FAI (Below 30): Investigate Other Causes
If your FAI is low but you are losing hair, other factors may be driving your loss:
- Thyroid dysfunction
- Iron deficiency
- Chronic telogen effluvium from stress or illness
- Autoimmune alopecia (areata)
Density tracking helps differentiate these patterns from androgenetic alopecia by revealing zone-specific loss patterns.
The DHT Sensitivity Spectrum
Even within a given FAI range, individual follicle sensitivity varies. This is determined by the androgen receptor (AR) gene on the X chromosome, which you inherit from your mother's side.
Tracking allows you to place yourself on the sensitivity spectrum empirically:
High sensitivity indicators (from tracking data):
- Rapid density decline (more than 5% per quarter) despite moderate FAI
- Loss concentrated heavily at the vertex (where androgen receptors are most dense)
- Poor response to finasteride alone (density continues to decline after 12 months on treatment)
Lower sensitivity indicators:
- Slow density decline (less than 2% per quarter) even with high FAI
- Loss primarily at the temples (less androgen receptor-dense area)
- Strong stabilization on finasteride within 6 months
Tracking Finasteride Response with Your FAI Data
When you start finasteride, your tracking data answers the critical question: is the DHT reduction sufficient for your personal sensitivity level?
Here is what to expect:
| Timeline | Expected Response (Responsive) | Red Flag (Non-Responsive) |
|---|---|---|
| Months 1 to 3 | Possible shedding (normal) | No change |
| Months 3 to 6 | Density stabilization | Continued decline over 3% |
| Months 6 to 12 | Mild improvement or stable | Decline exceeding 5% |
| Month 12+ | Stable or improved | Ongoing loss despite treatment |
If your density continues to decline after 12 months on finasteride, your FAI and tracking data together suggest that you may need a more aggressive anti-androgen approach, such as dutasteride, or combination therapy with minoxidil.
Take Action
Understanding your androgen profile turns hair loss treatment from guesswork into precision medicine. A blood panel costs $50 to $150 out of pocket, and the density data to correlate it with is available through your phone.
Start your free density analysis at myhairline.ai/analyze and pair it with your next blood panel to build your personal DHT sensitivity profile.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Blood test interpretation should be done by a qualified physician. Finasteride and dutasteride are prescription medications with potential side effects. Always consult a board-certified dermatologist or endocrinologist before starting or modifying any hormonal treatment.