Male Hair Loss: Causes, the Norwood Scale & Proven Treatments

How common is male hair loss?

Male hair loss — clinically known as androgenetic alopecia (AGA) or male pattern hair loss — is the most common cause of hair loss in men. The British Association of Dermatologists (BAD) estimates that approximately 50% of men are affected by the age of 50. Despite its prevalence, it can cause significant psychological distress, with studies consistently linking AGA to reduced self-esteem and social anxiety.

Causes: androgenetic alopecia explained

AGA is driven by dihydrotestosterone (DHT) — a potent androgen derived from testosterone by the enzyme 5-alpha reductase. In genetically predisposed men, DHT binds to androgen receptors in scalp hair follicles, causing follicular miniaturisation: the follicles progressively shrink, producing finer and shorter hairs before eventually ceasing production altogether.

NICE CKS confirms that AGA in men results from the combined effect of genetic predisposition and androgen activity, with the back and sides of the scalp typically spared due to follicles in these areas lacking androgen-sensitive receptors.

The Norwood-Hamilton scale

Hair loss severity in men is classified using the Norwood-Hamilton scale, which ranges from Stage I (minimal recession) to Stage VII (extensive baldness). Clinicians and prescribers use this classification to guide treatment decisions, as pharmacological treatments are most effective in earlier stages (I–IV).

Other causes of hair loss in men

NICE CKS advises clinicians to rule out alternative diagnoses before attributing hair loss solely to AGA. The following causes should be considered, particularly if hair loss is patchy, sudden, or accompanied by other symptoms:

• Telogen effluvium — diffuse shedding 2–3 months after a significant physiological stressor (illness, surgery, rapid weight loss, or nutritional deficiency); typically self-limiting and reversible
• Alopecia areata — autoimmune-mediated patchy hair loss; referral to dermatology is recommended by NICE CKS
• Thyroid dysfunction — both hypothyroidism and hyperthyroidism can cause hair thinning
• Iron deficiency anaemia — serum ferritin should be checked in men with diffuse hair loss of uncertain cause
• Medication side effects — anticoagulants, retinoids, and certain antidepressants are recognised causes in the BNF

Finasteride: the evidence

Finasteride 1 mg (licensed as Propecia; also available as a generic) is a 5-alpha reductase inhibitor that reduces scalp DHT levels by approximately 60–70%. It is a Prescription Only Medicine (POM) in the UK and is recognised by NICE CKS and the BNF as a licensed treatment for androgenetic alopecia in men.

According to the Electronic Medicines Compendium (EMC) Summary of Product Characteristics for finasteride 1 mg:

• Clinical trials demonstrated visible improvement in hair growth in the majority of men taking finasteride 1 mg after 12 months of continuous use
• Hair count increases of approximately 10% compared to baseline were observed at 12 months in placebo-controlled trials
• Hair loss resumed within 12 months of stopping treatment — confirming that ongoing use is required to maintain benefit
• Visible results typically require 3–6 months of consistent use
• Most effective at Norwood Stages I–IV
• Requires a valid prescription from a registered UK prescriber

Minoxidil: how it works

Topical minoxidil is the other MHRA-licensed treatment for male pattern hair loss in the UK. Originally developed as an oral antihypertensive, minoxidil in topical form is thought to act as a potassium channel opener, widening blood vessels around hair follicles, increasing blood and nutrient supply, and prolonging the anagen (growth) phase of the hair cycle.

The BNF lists minoxidil 2% and 5% topical solution and 5% topical foam as licensed treatments for AGA in men. The EMC SPC for Regaine for Men (minoxidil 5%) notes that in clinical trials:

• 5% minoxidil solution was statistically superior to 2% for hair regrowth at the vertex
• Hair regrowth was observed in the majority of users within 4–6 months of regular twice-daily application
• Hair loss resumed after stopping treatment, confirming that continuous use is needed
• Available without prescription in the UK (2% and 5% formulations)
• Applied directly to the dry scalp — twice daily (solution) or once daily (5% foam)

Finasteride vs minoxidil: side-by-side

Side effects and safety

Finasteride — MHRA and EMC SPC warnings

• Sexual side effects — including reduced libido, erectile dysfunction, and ejaculation disorders — are reported in a small proportion of users. The EMC SPC notes these are generally reversible on stopping treatment, but the MHRA has issued a Drug Safety Update noting rare reports of persistence after discontinuation
• Depression and mood change — the MHRA issued a safety update requiring patient information leaflets to include a warning about this risk
• PSA reduction — finasteride reduces serum PSA levels by approximately 50%. The BNF states that any PSA result in men taking finasteride should be doubled before comparison with normal ranges, to avoid masking prostate cancer

Minoxidil — EMC SPC and BNF

• Initial increased shedding may occur in the first 4–6 weeks as telogen hairs are displaced by new anagen growth — this is expected and not a sign of treatment failure
• Contact dermatitis to propylene glycol (in the solution formulation) is the most common adverse effect; the foam formulation avoids this excipient
• Systemic effects are rare with topical use at licensed doses, but the BNF advises avoiding application to broken or irritated skin

When to start treatment

The most important factor in treatment outcome is early intervention. Both MHRA-licensed treatments work most effectively at preserving existing follicles than restoring those that have been miniaturised for many years. NICE CKS and the BAD both note that earlier-stage AGA (Norwood I–III) responds best to pharmacotherapy.

Medicinex offers a confidential online consultation for finasteride prescriptions. All consultations are reviewed by our GPhC-registered prescriber team, and treatment is dispensed and delivered discreetly to your door.