Learn › Hair Loss

Hair Loss in Men: Causes, Types, and What Actually Works

By Truventa Medical Clinical Team · Updated April 2025 · 8 min read

Hair loss in men is extraordinarily common — affecting roughly 50% of men by age 50 and 85% by age 70 — but common doesn't mean you have to accept it. Understanding the root causes of male hair loss is the first step to making an informed decision about treatment, and the science behind what works is far clearer than most men realize.

The Root Cause: DHT and Androgenetic Alopecia

The vast majority of male hair loss — roughly 95% of all cases — is androgenetic alopecia, also called male pattern baldness (MPB). Despite what many people assume, it's not caused by "too much testosterone." It's caused by hair follicles that are genetically sensitive to a potent androgen called dihydrotestosterone (DHT).

What Is DHT?

DHT is a metabolite of testosterone. In various tissues throughout the body, the enzyme 5-alpha reductase (5-AR) converts testosterone into DHT. DHT is approximately 3–5 times more potent than testosterone at androgen receptors and plays important roles in prostate health, body hair growth, and male sexual development.

In men with genetically susceptible hair follicles, DHT binds to androgen receptors within the follicle and triggers a process called miniaturization:

1. The anagen (growth) phase of the hair cycle becomes progressively shorter
2. Each new hair grows thinner and lighter than the last
3. Eventually the follicle produces only a fine vellus hair (peach fuzz), then ceases producing hair entirely
4. The follicle shrivels but does not die — this is why early treatment can save follicles that are still active

Why Some Follicles and Not Others?

The key is androgen receptor density and 5-AR enzyme concentration in specific regions of the scalp. Follicles on the top and front of the scalp (the "androgenic zones") have significantly higher androgen receptor concentrations than those on the back and sides. This is why MPB follows predictable patterns — it spares the occipital and temporal zones that are androgen-insensitive.

Genetics and Inheritance

The susceptibility is primarily genetic. The androgen receptor gene is located on the X chromosome, which led to the popular belief that baldness "comes from your mother's side." While the maternal X is a significant contributor, research has identified over 250 genetic loci associated with androgenetic alopecia — meaning both parents contribute. If your father, maternal grandfather, and uncles all have significant MPB, your risk is substantially elevated.

The Norwood Scale: Staging Male Pattern Baldness

The Hamilton-Norwood scale classifies MPB into 7 stages:

• Type I: Minimal or no recession — essentially no hair loss
• Type II: Slight bilateral recession at the temples
• Type III: Deeper temporal recession, beginning to be cosmetically significant
• Type III Vertex: Loss primarily at the crown/vertex
• Type IV: More extensive frontal loss and vertex thinning, with a band of hair still separating them
• Type V: The separating band is thinning; frontal and vertex loss beginning to merge
• Type VI: Frontal and vertex zones fully merged, side and back hairline intact
• Type VII: Extensive loss, only a narrow horseshoe of hair remains at the sides and back

Treatment is most effective at Norwood Types II–IV. Once follicles have been miniaturized for years (Types VI–VII), the window for pharmacological reversal is largely closed — though regrowth at Type V is still possible with aggressive early treatment.

Other Causes of Hair Loss in Men

While androgenetic alopecia dominates, other causes account for the remaining 5% and can also co-occur alongside MPB. Identifying these is important because they require different treatments.

Telogen Effluvium

Telogen effluvium (TE) is the second most common cause of hair loss. It occurs when a physiological stressor triggers a large percentage of actively growing hairs to prematurely enter the resting (telogen) phase, causing widespread shedding 2–4 months after the triggering event.

Common triggers include:

• Major illness, surgery, or hospitalization
• Significant weight loss or crash dieting (protein/calorie restriction)
• Extreme psychological stress
• Thyroid dysfunction (both hypo- and hyperthyroidism)
• Iron deficiency anemia
• Post-COVID syndrome (hair loss is among the most commonly reported long-COVID symptoms)

The distinguishing characteristic: TE hair loss is diffuse (occurring all over the scalp), not patterned. It's also usually self-limiting — once the trigger is resolved, the hair cycle normalizes and most lost hair regrows within 6–12 months.

Alopecia Areata

Alopecia areata is an autoimmune condition in which the immune system attacks hair follicles, causing patchy, non-scarring hair loss. It affects approximately 2% of the population at some point in their lives. Patches are typically smooth, oval or round, and can appear anywhere on the scalp or body.

Most cases are limited in extent, but a minority progress to alopecia totalis (complete scalp hair loss) or alopecia universalis (complete body hair loss). Treatment options include corticosteroids (topical or injected), JAK inhibitors (newer class with impressive clinical results), and immunotherapy. This requires evaluation by a dermatologist.

Nutritional Deficiencies

Hair follicles are among the most metabolically active cells in the body and are correspondingly sensitive to nutrient deficiencies. Key deficiencies linked to hair loss:

• Iron: Even non-anemic iron deficiency (low ferritin without frank anemia) can cause significant shedding. Ferritin below 30–40 ng/mL is commonly associated with hair loss in both sexes.
• Zinc: Required for DNA synthesis and cell division in the rapidly dividing hair bulb
• Biotin: Deficiency is rare in people eating varied diets but causes diffuse hair loss when it occurs
• Vitamin D: Receptors for vitamin D are present in hair follicles; deficiency is common and may impair hair cycling
• Protein: The hair shaft is almost entirely keratin, a protein. Severe protein restriction causes dramatic shedding.

Thyroid Dysfunction

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) affect the hair cycle. Thyroid hormones regulate the transition between hair cycle phases, and abnormal thyroid function can cause diffuse shedding, dry brittle hair, and loss of the outer third of the eyebrow. TSH testing is a standard part of workup for unexplained hair loss.

Medications

Numerous medications list hair loss as a side effect:

• Anticoagulants (warfarin, heparin)
• Retinoids (isotretinoin/Accutane, acitretin)
• Certain blood pressure medications (beta-blockers, ACE inhibitors)
• Lithium and some anticonvulsants
• Chemotherapy agents (cause anagen effluvium — dramatic, rapid shedding)

What Doesn't Work for Male Hair Loss

Before discussing proven treatments, it's worth clearing away the noise. The hair loss industry generates billions in revenue from products with little to no evidence. Save your money and avoid:

• Shampoos claiming to "block DHT" or "stimulate growth": Topically applied compounds have negligible penetration to the follicle level. Ketoconazole shampoo has some modest evidence as an adjunct but is not a primary treatment.
• Biotin supplements in people without deficiency: If your biotin levels are normal, supplementing more doesn't help. The compelling before/after photos online are almost always from people who had biotin-deficiency-driven hair loss that would have resolved anyway.
• Scalp massagers and laser helmets (most consumer devices): Low-level laser therapy (LLLT) has some evidence but the evidence is weak and results modest. Consumer devices are largely unproven.
• Castor oil, rosemary oil, saw palmetto: Some very limited preliminary data exists for rosemary oil; the rest are not backed by quality clinical evidence.
• Vitamins, minerals, and "hair growth" supplements unless addressing a documented deficiency

What Actually Works for Hair Loss in Men

Two treatments have strong, decades-long evidence and FDA approval for male pattern hair loss. Both work through different mechanisms and are significantly more effective together than either alone.

Finasteride (Oral)

Finasteride is a 5-alpha reductase inhibitor that blocks the conversion of testosterone to DHT. At 1 mg daily (the approved hair loss dose), finasteride reduces scalp DHT levels by approximately 60–70%. Clinical trial results:

• 87% of men who took finasteride had no further hair loss at 2 years vs. placebo
• 66% experienced visible regrowth at 2 years
• Effects are maintained as long as the medication is continued
• Most effective at frontal and vertex loss; less effective at the hairline

Finasteride requires a prescription and is available through Truventa's hair loss program. The most discussed side effects — decreased libido, erectile dysfunction — occur in a small percentage of users (approximately 2–4%) and are reversible upon discontinuation in most cases. For the vast majority of patients, finasteride is well-tolerated long-term.

Minoxidil (Topical or Oral)

Minoxidil was originally developed as an oral blood pressure medication. Its ability to stimulate hair growth was discovered as a side effect. It works by prolonging the anagen (growth) phase of the hair cycle and improving blood flow to follicles. It does not affect DHT.

Topical minoxidil (2% or 5% solution/foam) applied once or twice daily produces meaningful regrowth or stabilization in approximately 60–70% of men. Oral minoxidil at low doses (1.25–5 mg/day) has emerged as a highly effective alternative for patients who dislike topical application, with clinical data showing superior results to topical in many studies. Oral minoxidil is now widely prescribed off-label for hair loss.

Combination Therapy

Studies consistently show that combining finasteride (which reduces DHT) with minoxidil (which stimulates follicle activity) produces significantly better results than either drug alone. Patients on combination therapy show the most robust regrowth, the best maintenance of existing hair, and the highest satisfaction rates. This is the gold standard approach for men serious about treating hair loss.

The Case for Treating Early

This is the single most important message for men concerned about hair loss: the earlier you treat, the better your outcomes.

Finasteride and minoxidil work by preserving and reactivating follicles that are still alive but being miniaturized by DHT. Once a follicle has been dormant long enough, it scars and cannot be reactivated by medication. At Norwood Type II–III, the vast majority of follicles are still salvageable. At Type V–VI, most are gone.

Men who start treatment at the first signs of thinning frequently maintain a full head of hair indefinitely. Men who wait until significant loss has occurred may achieve modest regrowth but cannot fully reverse years of follicle miniaturization. The best time to start was when you first noticed thinning. The second best time is now.

Visit our hair loss treatment page to learn more about how Truventa Medical can help you keep what you have and get back what you've lost.