Hair Transplant · Harley Street
What Causes Hair Loss?
The common reasons hair thins in men and women, and why identifying the cause changes the right treatment.
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Hair loss is not one condition. It can be inherited and permanent, or temporary and reversible once the trigger is addressed. Getting the cause right matters, because a transplant suits some causes and would be the wrong answer for others.
Below are the causes we see most often. The only way to know which applies to you is an assessment of your scalp, pattern and history.
Male and female pattern hair loss (and DHT)
The most common cause is androgenetic alopecia, or pattern hair loss. It is influenced by a hormone called DHT, which gradually shrinks sensitive follicles. In men it typically shows as a receding hairline and crown thinning; in women as a widening parting and diffuse thinning across the top, usually keeping the frontal hairline. Because the sides and back are generally DHT-resistant, they make a reliable donor area for a transplant.
Temporary and medical causes
Stress, illness, childbirth, crash dieting, low iron and thyroid problems can trigger a diffuse shedding (telogen effluvium) that often recovers once the cause is corrected. Autoimmune hair loss (alopecia areata) causes patchy loss, and tight styling can cause traction hair loss at the edges. These are assessed and, where possible, addressed before any thought of surgery.
Can diet and health cause hair loss?
Yes. Low iron, an under-active or over-active thyroid, rapid weight loss and some nutritional gaps can all thin the hair, usually as a diffuse shed rather than a receding pattern. The encouraging part is that this kind of loss often recovers once the underlying issue is addressed, which is why a proper history matters before anyone reaches for surgery.
Can hairstyles and treatments damage hair?
They can. Tight styles, extensions and harsh chemical processing put ongoing tension and stress on the follicles, and over years this can cause traction alopecia, particularly around the hairline and temples. Caught early it can improve by changing habits; left too long it can become permanent.
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Frequently asked questions
What is the most common cause of hair loss?
Pattern hair loss (androgenetic alopecia), driven partly by the hormone DHT, is by far the most common in both men and women. It is gradual and inherited, and it is the type most often suited to a hair transplant, because the sides and back usually stay resistant and provide donor hair.
Is my hair loss permanent or will it grow back?
It depends on the cause. Pattern hair loss is progressive and does not reverse on its own. Shedding from stress, illness, low iron or thyroid problems is often temporary and recovers once the trigger is treated. An assessment separates the two so you treat the right thing.
Can stress cause hair loss?
Yes. Significant physical or emotional stress can push hairs into a shedding phase, causing noticeable thinning a couple of months later. This type, telogen effluvium, usually recovers once things settle. Persistent or patterned loss, though, points to another cause worth assessing.
Does hair loss in women differ from men?
Often, yes. Women more commonly see diffuse thinning and a widening parting while keeping the frontal hairline, rather than a receding hairline. Causes such as hormonal changes, iron levels and thyroid function are important to check, which is why a tailored female assessment matters.
Can medication cause hair loss?
Some can, including certain treatments for blood pressure, mood and hormonal conditions, and this is usually reversible when the medication is reviewed. Never stop a prescribed medicine on your own; mention it at your assessment so we can factor it in.
How do I know which cause applies to me?
That is the point of an assessment. We look at the pattern, timing and pace of your loss alongside your health and family history, which usually points clearly to the cause and, importantly, to whether it is likely to recover or is here to stay.
Speak to our team
Every treatment begins with a free, no-obligation consultation at 19 Harley Street. We assess you in person and give honest advice on what suits you.
Medically reviewed by Dr Sumeyye Yuksel, MBBS · 24 July 2026