The causes of hair loss in men, and which ones a transplant can treat

Most of the causes of hair loss in men come down to one condition, androgenetic alopecia, which is genetic, hormonal and progressive, and which is the only common cause a transplant treats. The rest matter because they look similar in a mirror and behave completely differently: a thyroid problem, low iron, a stressful year, a new medication or an autoimmune condition can all thin your hair, and none of them is improved by moving follicles around. Telling them apart is the first job of any consultation, and it is done by pattern, by speed and by a few blood tests, not by a photograph alone.

Androgenetic alopecia

Genetic sensitivity to dihydrotestosterone; a recognisable pattern at temples, midline and crown; gradual over years; the transplant case

Telogen effluvium

Diffuse shedding two to four months after illness, surgery, crash dieting or a severe stressor; hair usually returns

Thyroid, iron, vitamin D, protein

Diffuse thinning with no pattern; corrected medically, not surgically

Medication and drugs

Some blood pressure, acne, antidepressant and anabolic agents shed hair; reversible on review with your prescriber

Alopecia areata

Sharply defined round patches, sometimes in the beard; autoimmune, not a surgical condition

Scarring alopecias and traction

Shiny skin with no follicular openings, or loss where hair is pulled tight; needs diagnosis before any surgery

Androgenetic alopecia: what is actually happening

Some follicles carry receptors that respond to dihydrotestosterone, a derivative of testosterone, by shortening their growth phase. Each cycle produces a slightly finer, shorter, less pigmented hair, until the follicle produces only a barely visible one and eventually nothing at all. That process is called miniaturisation and it is the whole disease.

Two things follow. The sensitivity is inherited, from both sides of the family rather than only from your mother’s father, so a bald maternal grandfather is evidence but not a verdict. And the sensitive follicles are distributed in a pattern, which is why the loss is recognisable: temples first, then the midline and the crown, with the band at the back and sides largely unaffected. The stages of that pattern are set out on the Norwood scale, and it is the pattern that makes surgery possible, because it leaves a donor area that is genetically immune to the same process.

The signs that your loss is not androgenetic

Four features point away from pattern loss and toward a medical cause.

Speed: pattern loss takes years, while something that arrived over six weeks is usually shedding, not miniaturisation. Distribution: pattern loss has a shape, whereas diffuse thinning across the whole scalp, including the back and sides, suggests a systemic cause. Shape of the bald area: sharply circular patches with smooth skin are typical of alopecia areata, not of pattern loss. Symptoms: burning, itching, tenderness, flaking or visible scarring point at an inflammatory scalp condition that has to be treated and stabilised first.

The practical test many men can do themselves is to look at the hair on the sides of the head. In androgenetic alopecia it stays dense. If it is thinning too, the cause is probably not androgenetic, and a transplant would be built on a donor that is itself failing.

Telogen effluvium, the common impostor

Hair grows in cycles, and a shock can push a large share of follicles into their resting phase at once. Two to four months later they shed together, which is why the trigger is usually forgotten by the time the hair falls. Typical triggers are a high fever or infection, major surgery, rapid weight loss, iron deficiency, a new medication, or a genuinely severe stressor such as a bereavement.

It looks alarming, with handfuls in the shower and hair on the pillow, but it is diffuse rather than patterned and it generally recovers once the trigger has passed. It also makes existing pattern loss look far worse than it is, which is the trap: many men book a surgical consultation during an effluvium and would be quoted a graft number they do not need. The correct answer is to wait, treat the cause and photograph the scalp every few months.

What a doctor checks before anyone discusses surgery

A dermatologist looks first, with a magnifier, for miniaturisation and for the density of follicular openings, because that distinguishes pattern loss from scarring loss in one minute. Then bloods: full blood count, ferritin, thyroid function, and vitamin D, with testosterone and other hormones where the picture suggests it. Your medication list is reviewed, including anabolic steroids and supplements, which patients rarely mention unprompted.

Which causes a transplant can and cannot treat

A transplant can treat stable androgenetic alopecia with a measurable donor area, scarring from injury or previous surgery once it is mature, and traction loss once the pulling has stopped. It cannot treat active alopecia areata, an untreated scarring alopecia, diffuse unpatterned loss, or thinning whose cause has not been identified. It also cannot treat a condition that is still moving quickly, which is a question of timing rather than of suitability; the rules are on the candidate page.

Where the cause is androgenetic, surgery and medication answer different questions. Surgery restores an area that has already gone. Medication protects what has not gone yet, and the case for it is on finasteride and minoxidil. Neither replaces the other, and a clinic that only ever recommends the one it sells is not giving you the full picture.

FAQ

How do I know if my hair loss is genetic?

Look for a pattern and a timescale. Recession at the temples, thinning along the midline or an opening crown, developing over years, with the sides and back staying dense, is the classic androgenetic picture. Diffuse thinning everywhere, rapid onset, round bald patches, or scalp symptoms point elsewhere. Family history on either side supports the diagnosis but does not make it. If there is any doubt, a dermatologist with a magnifier settles it in a single visit and blood tests fill in the rest.

Does stress cause hair loss in men?

A severe stressor can trigger telogen effluvium, a diffuse shed that appears two to four months later and usually resolves once the cause has passed. Ordinary daily stress does not cause pattern baldness, and stress does not convert a full head of hair into a receding hairline. What it does do is unmask progress that was already underway, which is why men often date their loss to a bad year. Treat the shed by treating the trigger, and judge the pattern afterwards.

Can hair loss be reversed without surgery?

Loss caused by iron deficiency, thyroid disease, a medication or a shedding episode often recovers fully once the cause is corrected, and that is genuine reversal. Androgenetic loss is different: medication can slow it and partly thicken hair that has miniaturised but not yet disappeared, and it cannot bring back a follicle that is gone. The earlier a medical decision is made, the more there is to protect, which is the main reason not to spend two years reading forums.

Is sudden hair loss on one side or in patches the same condition?

No. A sharply defined round patch, on the scalp or in the beard, with smooth skin and no follicular openings visible, is typical of alopecia areata, an autoimmune condition that is diagnosed and treated by a dermatologist and is not a surgical case, particularly while it is active. Loss confined to one side where you sleep, wear a cap or pull a hairstyle tight suggests traction or friction. Both need a diagnosis first, because operating on either would waste donor hair.

Clinically reviewed by the treating surgeon. Last reviewed 25 September 2026.