If you are a man in your thirties losing hair at the crown or temples, the odds favor androgenetic alopecia. The pattern is genetic, the mechanism is DHT-mediated, and the treatment is well-established.
The problem with that mental shortcut is that it skips the panel. When we evaluate hair loss, about one in five men has a meaningful secondary contributor. Sometimes the contributor is the whole story. More often it overlays androgenic loss and dampens the response to standard treatment. Either way, treating it changes the outcome.
What is non-androgenic hair loss?
Non-androgenic hair loss is hair shedding or thinning caused by something other than DHT-driven follicle miniaturization. The most common patterns in men we see are:
- Telogen effluvium. Diffuse shedding triggered by a stressor 2 to 4 months prior. Stressors include surgery, severe illness, weight loss, new medications, and psychological stress.
- Thyroid-driven hair loss. Both hypo- and hyperthyroid states cause hair thinning. Often diffuse rather than patterned.
- Iron deficiency. Low ferritin, even without anemia, is associated with diffuse hair thinning in observational data.
- Vitamin D deficiency. Linked to multiple hair-loss patterns, with the strongest association for telogen effluvium.
- Medication-induced. A long list, including some antidepressants, beta-blockers, statins, and finasteride itself in a small subset of users.
- Autoimmune. Alopecia areata is patchy rather than patterned and behaves differently from androgenic loss.
The reason this matters: a man with low ferritin and androgenic loss who starts finasteride alone will get a partial response and conclude the drug does not work for him. The drug is working. The deficit is undercutting it.
How does thyroid disease cause hair loss?
The thyroid sets the metabolic tempo for every tissue, including hair follicles. Hypothyroidism slows the active growth phase of the hair cycle and prolongs the resting phase. Hyperthyroidism, paradoxically, also drives hair shedding by pushing follicles into telogen prematurely.
The labs we check:
- TSH. The cleanest first signal. A TSH above about 4.5 mIU/L or below 0.4 mIU/L flags a thyroid contribution.
- Free T4. Confirms the central signal and rules out central hypothyroidism.
- Free T3. Useful when symptoms suggest a peripheral conversion issue.
- TPO antibodies. Identifies autoimmune (Hashimoto's) thyroiditis, which often presents subclinically before TSH moves much.
A "normal range" TSH is not the same as an optimal one for a given man. We pay attention to trends and to symptoms, not only to whether a value falls inside a wide reference interval.
How does iron deficiency cause hair loss?
Iron is a cofactor for ribonucleotide reductase, which is required for the rapid cell division in the hair-follicle matrix. Low ferritin (the storage form of iron) limits follicle growth even when hemoglobin is still in range.
The number to watch:
- Ferritin below 40 to 70 ng/mL. Multiple observational studies link this range to hair thinning in women and men, though the threshold debate is ongoing. Below 30 is more clearly associated with shedding.
- Iron saturation and TIBC. Useful when ferritin is borderline or when inflammation is suspected (ferritin is an acute-phase reactant and can be falsely elevated).
If ferritin is low, the next question is why. Dietary intake matters in men who have shifted toward plant-forward eating without supplementation. Blood loss from any source matters more. In a man over 40 with new iron deficiency, gastrointestinal evaluation is part of the workup, not optional.
How does vitamin D deficiency cause hair loss?
The vitamin D receptor is expressed in follicle cells, and vitamin D appears to play a role in follicle cycling. Deficiency (25-OH vitamin D below about 20 ng/mL) is linked to telogen effluvium and alopecia areata. The link to androgenic loss is weaker but present in observational data.
We aim for a 25-OH vitamin D in the 40 to 60 ng/mL range. Supplementation typically requires 2000 to 5000 IU daily of vitamin D3, with retesting at 3 months.
What about stress and telogen effluvium?
Telogen effluvium is diffuse shedding triggered by a stressor 2 to 4 months earlier. Common triggers include weight loss of more than about 5% of body weight, surgery, viral illness, new medications, and intense psychological stress.
The pattern is different from androgenic loss. Effluvium is diffuse across the scalp. Androgenic loss is patterned at the crown and temples. The two can coexist, particularly in men who lost meaningful weight on a GLP-1 or a deliberate cut.
Effluvium is self-limited. The shedding usually resolves within 3 to 6 months of the trigger being removed. Treatment is patient management of expectations and addressing the trigger. Finasteride does not fix it. Minoxidil can shorten the recovery.
What does the panel cost compared to the alternative?
A standard hair-loss panel costs in the range of $150 to $300 cash. The alternative is starting finasteride blind, running it for 9 months, getting a partial response, and asking why. By that point, you have spent more on the drug than the panel would have cost, and you still do not know what is going on.
A full picture of the markers we use across men's health is in the panel over 35.
How long do these contributors take to fix?
- Iron repletion. Ferritin usually rises within 8 to 12 weeks with adequate oral supplementation. Hair response lags by another 2 to 4 months.
- Vitamin D. Levels respond within 8 to 12 weeks. Hair response follows the same delay as iron.
- Thyroid. Symptom response to thyroid replacement can take 6 to 12 weeks. Hair response can take 3 to 6 months.
- Telogen effluvium. Self-limited within 3 to 6 months of the trigger resolving.
The hair cycle is slow. None of these is a fast fix. But none of them require a daily prescription, either.
Where Vane lands
The hair conversation should start with labs, not with a prescription. Most of the men we put on finasteride and minoxidil needed those drugs. A meaningful share also needed something else first, and the something else was usually cheap, fixable, and would have been missed by a quiz.
A panel before a prescription is the cleanest way to make sure the drug you start does the work it should.
