Published on:
March 6, 2026
Hair loss is one of the most common concerns patients bring to their GP, yet it remains widely misunderstood. Many people assume it is a condition that affects only older men, but the reality is far more nuanced. Women account for a significant proportion of hair loss cases, and the underlying drivers of female and male hair loss differ in important ways — even when the end result looks similar.
Whether you are noticing a widening parting, a receding hairline, or simply more hairs on your pillow each morning, understanding why hair loss occurs is the essential first step towards effective treatment. The causes range from hormonal imbalances and genetic predisposition to nutritional deficiencies, stress, and autoimmune conditions. In this article, we explore each of these drivers in depth, explain how they differ between the sexes, and outline when it is time to seek professional advice.
If you are already concerned about thinning hair, our dedicated hair loss service can help you identify the cause and discuss your options with an experienced clinician.
Androgens — the group of hormones that includes testosterone — are the single most important hormonal driver of hair loss in men. Specifically, researchers have identified dihydrotestosterone (DHT) as the key culprit. DHT is produced when the enzyme 5-alpha reductase converts testosterone into its more potent form. In genetically susceptible hair follicles, DHT binds to androgen receptors and gradually shrinks the follicle in a process known as miniaturisation. Over time, the affected follicles produce thinner, shorter hairs until they eventually stop producing visible hair altogether.
This process typically follows a recognisable pattern in men: recession at the temples and thinning at the crown, eventually progressing to more extensive baldness. The Hamilton–Norwood scale is commonly used to classify the stages. Crucially, not every man with high testosterone levels will lose his hair — it is the sensitivity of follicles to DHT, determined largely by genetics, that dictates who is affected.
Androgens also play a role in female pattern hair loss (FPHL), but the relationship is more complex and less well understood. While some women with FPHL show elevated androgen levels — often associated with conditions such as polycystic ovary syndrome (PCOS) — many have entirely normal hormone profiles. This suggests that additional mechanisms beyond androgen activity are at work in women.
The pattern of hair loss in women also differs. Rather than a receding hairline, women typically experience diffuse thinning across the top and crown of the scalp, often described as a widening of the central parting. The frontal hairline is usually preserved. Researchers believe that while FPHL and male balding share a common final pathway of follicular regression, the aetiologies are not necessarily identical in both sexes.
For women experiencing hair changes during midlife, hormonal shifts associated with the menopause and hormone replacement therapy (HRT) can be a significant factor. The decline in oestrogen relative to androgens during perimenopause can unmask a genetic tendency towards hair thinning, making this a particularly common time for women to first notice hair loss.
Androgenetic alopecia — the medical term for pattern hair loss — is, by definition, a condition with a strong genetic component. Genome-wide association studies have identified numerous genetic variants linked to hair loss risk, many of which are located on the X chromosome. This is why it has long been observed that male pattern baldness often runs along the maternal line, although paternal genes also contribute.
A positive family history remains one of the strongest predictors of hair loss in both men and women. If your mother, father, or close relatives experienced significant thinning, your own risk is elevated. However, genetics does not operate in isolation; it interacts with hormonal, environmental, and lifestyle factors to determine the onset, speed, and severity of hair loss.
Hair loss is a polygenic trait, meaning it is influenced by multiple genes rather than a single one. This makes it difficult to predict with certainty who will be affected and to what degree. Some individuals may carry a higher genetic load but never develop noticeable hair loss because protective factors — hormonal balance, good nutrition, low stress — keep the condition at bay. Others with a seemingly modest genetic risk may experience significant thinning if environmental triggers are present.
Current research continues to identify new genetic loci associated with hair loss, and it is hoped that in the future, genetic profiling may allow for earlier identification of at-risk individuals and more personalised treatment approaches.
Nutritional deficiencies are a frequently overlooked driver of hair loss, particularly in women. Iron deficiency — with or without frank anaemia — is one of the most common nutritional causes of excessive hair shedding. Iron is essential for the production of haemoglobin, which carries oxygen to cells, including the rapidly dividing cells of the hair follicle. When iron stores are depleted, the body prioritises vital organs over hair growth, leading to a form of hair loss known as telogen effluvium.
Other nutrients implicated in hair health include zinc, biotin, vitamin D, and essential fatty acids. Restrictive diets, eating disorders, and malabsorption conditions such as coeliac disease can all contribute to deficiency-driven hair loss. A simple blood test can identify most nutritional shortfalls, making this one of the more treatable causes of thinning.
Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can cause diffuse hair loss. The thyroid gland produces hormones that regulate metabolism throughout the body, and disruptions to this delicate balance affect the hair growth cycle. Hair may become dry, brittle, and prone to breakage, and shedding may increase significantly. Thyroid-related hair loss is more common in women and is often reversible once the underlying thyroid condition is properly managed.
A history of thyroid dysfunction is commonly noted alongside pattern hair loss, and clinicians should screen for thyroid disorders in any patient presenting with unexplained hair thinning.
Telogen effluvium is a form of temporary, diffuse hair loss triggered by a significant physiological or emotional stressor. Common triggers include surgery, severe illness, high fever, rapid weight loss, childbirth, and intense psychological stress. The mechanism is straightforward: the stressor pushes a larger-than-normal proportion of hair follicles into the telogen (resting) phase simultaneously. Two to three months later, these hairs are shed, often resulting in alarming levels of hair fall.
The good news is that telogen effluvium is usually self-limiting. Once the underlying stressor is resolved, normal hair growth typically resumes within six to twelve months. However, chronic or repeated stress can lead to a prolonged form of the condition, known as chronic telogen effluvium, which may persist for years.
Certain medications are well-known drivers of hair loss. Chemotherapy drugs, which target rapidly dividing cells, can cause anagen effluvium — a sudden and often complete loss of hair during the active growth phase. Other medications associated with hair thinning include anticoagulants such as warfarin, retinoids used to treat acne (e.g., isotretinoin), beta-blockers, certain antidepressants, and some hormonal contraceptives.
If you suspect a medication is contributing to your hair loss, it is important to discuss this with your doctor rather than stopping treatment abruptly. In many cases, alternative medications can be considered, or the hair loss may resolve once the course of treatment is completed.
Beyond medical causes, everyday lifestyle factors can contribute to hair thinning. Excessive heat styling, chemical treatments, and tight hairstyles (such as braids, ponytails, or extensions) can cause a form of hair loss known as traction alopecia, which can become permanent if sustained over long periods. Smoking has also been linked to accelerated hair loss, likely due to its effects on blood flow to the scalp and oxidative stress on follicles.
Chronic sleep deprivation, poor diet quality, and excessive alcohol consumption may also indirectly worsen hair loss by disrupting hormonal balance and nutrient absorption. Addressing these modifiable risk factors is an important part of any comprehensive hair loss management plan.
Alopecia areata is an autoimmune condition in which the body's immune system mistakenly attacks hair follicles, causing hair to fall out in small, round patches. It can affect men, women, and children at any age, and in severe cases, it may progress to total scalp hair loss (alopecia totalis) or complete body hair loss (alopecia universalis).
The exact triggers for alopecia areata are not fully understood, but the condition is more common in individuals with a personal or family history of other autoimmune diseases, such as thyroid disorders, vitiligo, or type 1 diabetes. Treatment options range from topical corticosteroids to newer immunotherapy agents, and the prognosis varies widely between individuals.
A less common but more serious group of conditions, the scarring (cicatricial) alopecias, involve inflammation that destroys the hair follicle and replaces it with scar tissue. Unlike androgenetic alopecia or telogen effluvium, scarring alopecias result in permanent hair loss in the affected areas. Examples include lichen planopilaris, frontal fibrosing alopecia, and discoid lupus erythematosus. Early diagnosis and treatment are critical to halt progression and preserve as much hair as possible.
While many of the underlying drivers of hair loss are shared between the sexes, the way hair loss presents — and the relative importance of each driver — differs significantly between women and men.
In men, androgenetic alopecia is overwhelmingly the most common cause, typically beginning in the late teens or twenties and progressing with age. The pattern is usually predictable: temporal recession and vertex thinning. Androgens, and specifically DHT, are considered necessary for male pattern hair loss to develop, and this strong hormonal link has made anti-androgen therapies such as finasteride a cornerstone of treatment.
In women, the picture is more multifactorial. While FPHL is the most common diagnosis, women are more likely than men to experience hair loss driven by nutritional deficiencies, thyroid disorders, hormonal fluctuations related to pregnancy and menopause, and autoimmune conditions. The diffuse thinning pattern seen in FPHL can also overlap with telogen effluvium, making diagnosis more challenging. If you are a woman experiencing hair thinning, our female hair loss page provides further information on the conditions we treat and the diagnostic approach we take.
Another important distinction is the psychological impact. Research consistently shows that hair loss can cause significant emotional distress in both sexes, but societal expectations around female hair often mean that women experience particularly high levels of anxiety and reduced self-esteem. This makes compassionate, thorough clinical assessment all the more important.
It is normal to lose between 50 and 100 hairs per day as part of the natural hair growth cycle. However, you should consider seeing a clinician if you notice a sudden increase in hair shedding, visible thinning or bald patches, a receding hairline, or hair loss accompanied by other symptoms such as fatigue, weight changes, or skin problems.
A thorough clinical assessment typically includes a detailed medical history, examination of the scalp, and blood tests to check for hormonal imbalances, nutritional deficiencies, and thyroid function. In some cases, a scalp biopsy or trichoscopy (a specialised examination of the hair and scalp under magnification) may be recommended to confirm the diagnosis.
Early intervention is key. Many forms of hair loss respond best to treatment when caught early, before significant follicular miniaturisation or scarring has occurred. Whether the cause turns out to be hormonal, nutritional, autoimmune, or stress-related, identifying the specific driver is essential for choosing the right treatment strategy.
The most common cause of hair loss in men is androgenetic alopecia, also known as male pattern baldness. It is driven primarily by the hormone dihydrotestosterone (DHT) acting on genetically susceptible hair follicles. This leads to progressive miniaturisation of follicles, typically starting with recession at the temples and thinning at the crown.
During menopause and perimenopause, oestrogen levels decline while androgen levels remain relatively stable. This shift in the oestrogen-to-androgen ratio can unmask a genetic predisposition to hair thinning, leading to female pattern hair loss. Hormonal therapies may help in some cases — speak to your clinician about whether this is appropriate for you.
Yes. Iron deficiency is one of the most common nutritional drivers of hair loss, particularly in women. Deficiencies in zinc, vitamin D, biotin, and essential fatty acids can also contribute. A blood test can identify these shortfalls, and correcting the deficiency often leads to improvement in hair growth over several months.
In most cases, stress-related hair loss — known as telogen effluvium — is temporary. Once the underlying stressor is resolved, hair growth typically returns to normal within six to twelve months. However, chronic or repeated stress can prolong the condition, so addressing the root cause is important.
You should seek professional advice if you notice a sudden or significant increase in hair shedding, visible thinning or bald patches, or if your hair loss is accompanied by other symptoms such as fatigue or weight changes. Early assessment allows for timely diagnosis and the best chance of effective treatment.
The information provided in this article is for educational purposes only and is based on NHS recommendations. It is not a substitute for professional medical advice. Always consult your doctor or a qualified healthcare provider for advice on medical conditions or treatments.
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