The 5 Main Causes of Hair Loss in Men

Some causes are temporary and reversible, while others are long-term but can now be managed very effectively. Here are the five main causes of male hair loss, explained simply, along with what the medical literature really says about each one.

First things first: understanding the hair cycle

A hair does not grow continuously. It follows a three-stage cycle: an active growth phase, known as anagen, which lasts two to six years, a short transition phase of three weeks, then a resting phase of two to three months, at the end of which the hair falls out to make way for a new one.

On a healthy scalp, around 85% of hairs are growing and 15% are resting. Losing 50 to 100 hairs a day is perfectly normal. This is why shedding can look dramatic in the sink without being abnormal, and why a genuine loss of density can set in without you ever seeing much hair fall out.

This distinction is essential. Shedding and loss of density are two different phenomena, with different causes, and they are often confused.

1. Genetics and hormones: androgenetic alopecia

This is by far the most common cause. Around one man in two is affected by the age of 50, and nearly 80% by the age of 70.

What DHT does to the follicle

At play is an inherited sensitivity of the follicles to a hormone derived from testosterone: dihydrotestosterone, or DHT. In the affected areas, three things are observed at once: increased DHT production, high levels of the enzyme that produces it, and a greater density of androgen receptors.

The process is gradual. With each cycle, the growth phase becomes shorter. The follicle produces a slightly finer, slightly shorter hair, until it produces nothing but fine, downy hair, and then nothing at all. This is known as miniaturisation. The hair loss follows a recognisable pattern: receding temples first, then the crown.

One clinical observation confirms the causal role of DHT: men born with a deficiency in the enzyme that produces it never develop baldness.

Why the hair at the back of the head holds out

This is the point that makes a transplant possible, and it is worth understanding. Sensitivity to androgens is an intrinsic property of the follicle, not of the area of the scalp where it sits. The follicles in the occipital band at the back of the head are genetically resistant, and they remain so wherever they are placed.

This is known as the principle of donor dominance, and it is the biological foundation of FUE hair transplantation: we do not create new hair, we redistribute resistant follicles to the thinning areas.

There is, however, an honest nuance to add. A histological study of 82 men showed that in the most advanced stages of baldness, miniaturisation also begins to affect the occipital area. This is one of the reasons why a careful examination of the donor area is part of any serious diagnosis, not just an assessment of the area to be covered.

No, baldness does not only come from your mother's side

This is the most persistent myth on the subject. It does contain a grain of truth: the androgen receptor gene is indeed carried on the X chromosome, inherited from the mother, and it is the single most important determining factor.

But the largest genetic study conducted to date, involving more than 200,000 men, identified 624 regions of the genome involved, 598 of them on the non-sex chromosomes. Inheritance is polygenic and comes from both parents. A son whose father was affected has a five to six times higher risk.

2. Stress and emotional shocks

Intense stress, surgery, a high fever, an illness or sudden weight loss can trigger telogen effluvium: a large number of hairs switch prematurely into the resting phase and fall out diffusely.

The link almost nobody makes: the hair loss occurs with a delay of two to four months after the triggering event, sometimes longer. By the time patients seek advice, they have often forgotten the episode responsible and look for an explanation in their current circumstances.

Unlike androgenetic alopecia, this type of hair loss is usually temporary and reversible once the cause is under control, with density returning to normal within six to nine months. It is worth knowing, however, that around a third of cases of telogen effluvium have no identifiable cause, and that stress is very often blamed by default.

3. Nutritional deficiencies: what is true and what is less so

Hair needs nutrients to grow, and protein malnutrition or severe dietary restriction has a direct impact on density. That much is established.

Beyond that, the literature is far more cautious than marketing claims, and we believe it is only honest to say so.

• Iron. A severe iron deficiency can contribute to hair loss. However, a study of 181 women found no correlation between ferritin levels and the proportion of hairs in the resting phase, and the authors concluded that the role of iron status has probably been overestimated.
• Zinc. The data are considered insufficient to recommend supplementation.
• Vitamin D. There is a real signal in alopecia areata, but the data are contradictory for androgenetic alopecia.
• Biotin. Its effectiveness is not supported outside a documented deficiency. Worse still, excess biotin can distort certain blood tests, with reported medical consequences.

A point rarely mentioned: too much can also cause hair loss. A vitamin A intake above 10,000 units a day, or an excess of selenium, are themselves documented causes of hair loss. Taking supplements without prior testing is therefore not without consequence.

4. Lifestyle and aggravating factors

Some habits cannot explain hair loss on their own, but they can worsen or accelerate it:

• Smoking, which reduces microcirculation in the scalp
• Lack of sleep
• Chronic stress
• Excess alcohol, pollution and oxidative stress

Smoking is the factor whose effect has been most clearly quantified. A meta-analysis combining eight studies found that smokers have a risk of androgenetic alopecia around 1.8 times higher, as well as an increased risk of progressing to advanced stages. This is a statistical association, not proof of causation, but it is consistent from one study to the next.

Addressing these factors will not make a hair that is programmed to fall out grow back. It does, however, preserve your existing hair and optimise the results of any hair loss treatment.

5. Medical causes and certain treatments

Some hair loss has a medical origin that is important to identify, as the right approach depends entirely on the cause.

• Thyroid disorders. In a series of 460 patients with hypothyroidism, diffuse hair loss was present in 46% of them. Thinning of the outer third of the eyebrows is a classic warning sign.
• Alopecia areata, also known as patchy hair loss. An autoimmune condition affecting around 2% of the population during their lifetime, it appears as well-defined bald patches. Spontaneous regrowth occurs in 80% of patients within the first year.
• Medication. Anticoagulants, beta blockers, anti-epileptics, lithium, retinoids, interferons and anti-inflammatories are among the classes involved, with visible hair loss two to four months after starting treatment. Anabolic steroids are also implicated, a common concern among young, athletic men.
• Scarring alopecias, such as lichen planopilaris. These permanently destroy the follicle. This is the only case where the time taken to seek advice truly changes the outlook, because what is lost does not come back.

Finally, traction alopecia, a mechanical hair loss caused by tight hairstyles or by wearing very close-fitting headwear for long periods, is very real and remains reversible if it is caught in time.

Normal shedding or hair loss worth worrying about?

A few simple guidelines. Losing 50 to 100 hairs a day is normal. More noticeable seasonal shedding in late summer and early autumn is a documented and harmless phenomenon.

What warrants medical advice:

• sudden, diffuse hair loss, especially if it lasts more than six months
• well-defined bald patches
• a scalp that is red, painful, itchy or flaky
• a visible loss of density within a few months in a young man
• hair loss accompanied by fatigue, or by unexplained weight gain or loss

An often overlooked health signal

A little-known yet well-documented point: a meta-analysis of 19 studies and more than 2,500 participants revealed a significant association between androgenetic alopecia and metabolic syndrome, with a risk around 3.5 times higher. The association is even stronger in cases of early baldness.

This is an association, not a cause-and-effect relationship, and there is no reason for alarm. It does suggest, however, that early baldness warrants at the very least a check of blood pressure, blood sugar and blood lipids. It is the kind of thing a conscientious practitioner will raise, and that a purely commercial centre never will.

How can you find out what is causing your hair loss?

The same hair loss can hide very different causes, and often several at once. Identifying yours is the first step towards choosing the right response: a simple rebalancing, medical treatment, or a hair transplant when the loss is permanent.

The diagnosis of typical androgenetic alopecia is clinical. It relies on examining the scalp, observing the pattern of hair loss and a magnified analysis that reveals miniaturisation. Contrary to what is often written, no blood test is needed in this classic form. Diffuse, sudden or atypical hair loss, on the other hand, fully justifies further tests.

Beyond the hair analysis, the conversation with the doctor matters just as much. Family history, lifestyle, diet, stress levels, sleep, current treatments, significant events in recent months: it is often these elements, pieced together, that reveal the true cause.

At New Hair Graft in Mauritius, we always begin by understanding the cause of your hair loss before recommending anything. If a transplant is not the right solution for you, we will tell you. Book your free hair diagnosis, or start by exploring the common myths about hair transplants.