Understanding Hair Loss in Men: Causes, Types and When to Act

Finding more strands on your pillow or noticing your hairline creeping backwards is one of the most common reasons men in Singapore book a consultation for hair loss. Hair may seem like a purely cosmetic feature, but for most men it is tied closely to confidence, perceived youthfulness and self-image. The good news is that most hair loss follows recognisable patterns, and an SMC-registered doctor can usually tell within a single consultation whether you are dealing with a genetic condition, a temporary shedding phase, or something else entirely.

This article explains how hair grows, what androgenetic alopecia actually is, how it differs from telogen effluvium, and when it is worth seeing a doctor rather than waiting it out.

How healthy hair grows

Every hair follicle on your scalp cycles through distinct phases throughout your life. Understanding this cycle makes it much easier to understand what goes wrong in hair loss conditions.

1. Anagen (growth phase) - This is the active growth phase, lasting roughly two to six years on the scalp. At any given time, about 85-90% of scalp hairs are in this phase, which is why healthy scalps can grow hair to considerable lengths.
2. Catagen (transition phase) - A short two to three week phase where the follicle shrinks and detaches from its blood supply. Only around 1% of hairs are in this phase at any time.
3. Telogen (resting phase) - The hair remains dormant in the follicle for about three months before being shed. Roughly 10-15% of scalp hairs sit in this phase normally.
4. Exogen (shedding phase) - The old hair is released and a new anagen hair begins growing in its place. Shedding 50 to 100 hairs a day during this phase is entirely normal.

Problems arise when this balance is disrupted - either because a larger-than-normal proportion of follicles are pushed into the telogen phase (as in telogen effluvium), or because the follicles themselves progressively shrink over successive cycles (as in androgenetic alopecia).

What is androgenetic alopecia?

Androgenetic alopecia, commonly called male or female pattern hair loss, is by far the most common cause of hair thinning worldwide, and Singapore is no exception. Studies on Asian populations suggest slightly lower prevalence and later onset compared to Caucasian men, but it still affects a substantial proportion of men by midlife, with rates climbing steeply after age 40.

The condition used to be called "androgenic" alopecia, implying a purely hormonal cause. Research has since shown that genetics plays an equally important role, which is why the term androgenetic alopecia is now preferred - it reflects the interplay between inherited follicle sensitivity and androgen hormones.

In affected follicles, the normal 12:1 ratio of anagen to telogen hairs can shift dramatically, sometimes to as low as 5:1. Each growth cycle produces a slightly thinner, shorter hair than the one before - a process called miniaturisation. Over years, this turns thick terminal hairs into fine, barely visible vellus-like hairs, and eventually the follicle may stop producing visible hair altogether.

The role of DHT and genetics

The key biological driver is dihydrotestosterone (DHT), a potent metabolite of testosterone. The enzyme 5-alpha-reductase converts testosterone into DHT within the skin and hair follicles. In men who are genetically predisposed, scalp follicles in the frontal and crown regions carry androgen receptors that are unusually sensitive to DHT, triggering the miniaturisation process described above. This genetic sensitivity is inherited polygenically, meaning it can come from either side of the family - the old idea that baldness is inherited only from your mother's father is a myth.

Interestingly, DHT sensitivity varies by scalp location. Follicles at the back and sides of the scalp are typically resistant to DHT, which is why hair transplant surgery relies on moving follicles from these "donor" zones to balding areas.

The Norwood scale: tracking the pattern

Doctors and hair restoration specialists use the Norwood-Hamilton scale to classify the severity and pattern of male hair loss, ranging from Stage 1 (no visible loss) through to Stage 7 (extensive loss leaving only a horseshoe-shaped band of hair at the back and sides).

Norwood stage	Typical presentation	General treatment window
Stage 1-2	Minimal recession at the temples	Excellent response to medical therapy
Stage 3	Distinct temporal recession, early crown thinning	Good response, early intervention advised
Stage 4	Frontal and crown thinning with a persisting band of hair between them	Moderate response; medical therapy with structured photographic review
Stage 5	The band between frontal and crown loss narrows further	Medical therapy stabilises rather than reverses; transplant often discussed
Stage 6-7	Frontal and crown areas merge into extensive baldness	Limited regrowth potential; surgical options considered

Recognising your own stage on this scale helps set realistic expectations. Medical treatments tend to work best at slowing progression and thickening miniaturised hairs at Stages 1 to 4, which is why earlier consultation generally produces better long-term outcomes.

Androgenetic alopecia vs telogen effluvium

Not all hair thinning is androgenetic alopecia. One of the most important distinctions a doctor will make is between androgenetic alopecia and telogen effluvium, since the two conditions require completely different management.

Telogen effluvium is a diffuse, temporary shedding condition triggered by physiological stress - this could be a high fever, major surgery, significant weight loss, childbirth, severe emotional stress, thyroid dysfunction, iron deficiency, or starting or stopping certain medications. It typically appears two to three months after the triggering event, as a large cohort of follicles are prematurely pushed from the anagen into the telogen phase simultaneously. Hair falls out diffusely across the whole scalp rather than in a defined pattern, and shedding is usually more dramatic - handfuls of hair rather than gradual thinning.

Androgenetic alopecia, by contrast, develops gradually over months to years, follows a predictable pattern (frontal recession and crown thinning in men), and does not resolve on its own without treatment.

Feature	Androgenetic alopecia	Telogen effluvium
Onset	Gradual, over years	Sudden, weeks after a trigger
Pattern	Frontal hairline and crown	Diffuse, whole scalp
Underlying cause	Genetic sensitivity to DHT	Physiological stressor or illness
Natural resolution	Does not reverse without treatment	Often self-resolves in 3-6 months
Hair miniaturisation	Present, visible on close exam	Absent - hairs are normal calibre

Because the two conditions can occasionally overlap - stress can accelerate an existing genetic predisposition - a proper clinical assessment is important rather than assuming either diagnosis based on symptoms alone.

How hair loss is diagnosed

A consultation for hair loss at Hisential typically begins with a detailed history: when the shedding started, family history of baldness, recent illnesses, medications, diet, and stress levels. This is followed by a close scalp examination, sometimes with a dermatoscope, to check for miniaturisation, scalp inflammation, or scarring.

Blood tests are sometimes ordered to rule out reversible contributors such as iron deficiency, thyroid dysfunction, or, in the context of a broader health screening, other metabolic issues that can accelerate hair thinning. In men with symptoms suggestive of low hormone levels, a workup for testosterone deficiency may also be considered, since hormonal imbalances can influence hair health alongside libido, energy and mood.

Doctors do not usually need a scalp biopsy to diagnose typical androgenetic alopecia, but it may occasionally be used if the diagnosis is unclear or there are signs of scarring alopecia.

Other, less common causes of hair thinning

While androgenetic alopecia and telogen effluvium account for the majority of cases seen in clinic, a smaller proportion of men present with other conditions that mimic pattern hair loss. Alopecia areata causes sudden, well-demarcated round patches of hair loss due to autoimmune attack on follicles, and usually looks quite different from the gradual frontal-crown thinning of androgenetic alopecia. Fungal scalp infections (tinea capitis) can cause patchy hair loss with scaling and itching, and require antifungal treatment rather than hair growth medication. Traction alopecia, from tight hairstyles or headwear worn constantly, causes gradual thinning at the margins of the scalp where tension is greatest. Recognising these less common patterns is another reason a clinical assessment is valuable rather than self-diagnosing based on internet searches alone.

Why acting early matters

Follicles that have been miniaturising for years without treatment eventually lose the capacity to regrow thick terminal hair, even with medication. This is because prolonged DHT exposure can lead to progressive fibrosis around the follicle. Once a follicle is scarred over, no topical or oral medication can revive it - only a transplant, which moves a healthy follicle into that space, can restore hair growth there.

This is why doctors generally recommend starting treatment as soon as thinning is noticed, rather than waiting until hair loss is advanced. Early Norwood stages respond far better to oral and topical medications, and there is simply more follicle "reserve" left to protect. For men who are already at Norwood Stage 4 or beyond, treatment can still meaningfully slow the process and thicken remaining hairs, but full reversal becomes less realistic.

If you are unsure which category your hair loss falls into, a consultation is often more useful than months of guessing with over-the-counter products. To understand the specific treatment options available - from topical minoxidil to oral 5-alpha-reductase inhibitors and regenerative injections - see our detailed guide on managing androgenetic alopecia.

Common questions

Is hair loss in your 20s normal?

It can be. Androgenetic alopecia can begin as early as the late teens or twenties in genetically predisposed men, and early onset is often associated with a stronger family history. It is not something to dismiss as "too young" - early treatment tends to give the best long-term results.

Can stress alone cause permanent baldness?

Stress-related shedding (telogen effluvium) is usually temporary and resolves once the underlying trigger is addressed, typically within three to six months. However, chronic, ongoing stress can sometimes unmask or accelerate an underlying genetic predisposition to androgenetic alopecia, so persistent shedding beyond six months should be assessed by a doctor.

Does wearing caps or helmets cause hair loss?

There is no strong scientific evidence that wearing hats or helmets causes androgenetic alopecia. This is a persistent myth. Genetics and DHT sensitivity remain the dominant drivers of pattern hair loss.

How much hair loss is normal per day?

Losing 50 to 100 hairs a day is considered normal as part of the natural growth cycle. Consistently shedding more than this, or noticing visible thinning over weeks to months, warrants an evaluation.

Should I see a doctor or try over-the-counter products first?

Over-the-counter shampoos and supplements rarely address the underlying hormonal or genetic drivers of pattern hair loss. A consultation (from S$50 after GST) allows a doctor to confirm the diagnosis and start evidence-based treatment before follicles are lost, which is far more cost-effective than years of ineffective products.

Can hair loss indicate a more serious underlying health issue?

Occasionally. Sudden, diffuse hair loss can be linked to thyroid disorders, iron deficiency, or nutritional issues, which is why a broader nutritional screening or blood workup is sometimes recommended alongside a scalp examination, particularly if the pattern does not fit typical androgenetic alopecia.