Published on:
March 6, 2026
Hair loss is one of the most common concerns raised in general practice, yet it remains widely misunderstood. Many people assume it is a condition that only affects men, but research consistently shows that up to 50 per cent of women will experience noticeable hair thinning at some point in their lives. Understanding the drivers of female and male hair loss is the essential first step towards effective management — because the underlying causes differ between the sexes, and even between individuals of the same sex.
Whether you are noticing a receding hairline, a widening parting, or simply more hair in the shower drain, knowing why it is happening empowers you to seek the right help at the right time. In this article, we explore the hormonal, genetic, nutritional, and lifestyle factors that contribute to hair loss in both women and men, and outline when it may be time to speak to a specialist. If you are already concerned about thinning, our dedicated hair loss service is a good place to start.
Androgenetic alopecia — commonly known as male pattern baldness — is the single most prevalent form of hair loss in men, responsible for over 95 per cent of cases. At its core is a hormone called dihydrotestosterone (DHT). DHT is derived from testosterone via the enzyme 5-alpha reductase, and it binds to androgen receptors in susceptible hair follicles on the scalp. Over time, this binding causes the follicles to miniaturise, producing thinner, shorter hairs until growth effectively ceases.
The pattern is characteristically predictable: thinning typically begins at the temples and crown, gradually progressing to leave a horseshoe-shaped rim of hair around the sides and back of the head. Importantly, the follicles on the sides and back of the scalp lack the same density of androgen receptors, which is why they are more resistant to DHT-driven loss.
In women, the picture is more nuanced. Androgens are involved in female pattern hair loss (FPHL) in some cases, but research suggests that they are not always the primary driver. As noted by researchers at the National Institutes of Health, "androgens are a key driver of male balding and also involved in the etiology of pattern hair loss in some women," but the two conditions do not share identical pathways. Women with FPHL typically experience diffuse thinning across the top of the scalp, with the frontal hairline usually preserved — a markedly different presentation to the male pattern.
Hormonal shifts play a particularly significant role in women. Fluctuations during pregnancy, the postpartum period, perimenopause, and menopause can all trigger or accelerate hair thinning. The decline in oestrogen and progesterone during menopause, for example, may unmask the effects of circulating androgens, leading to a relative androgen excess even when absolute androgen levels remain normal. Conditions such as polycystic ovary syndrome (PCOS), which is characterised by elevated androgen levels, are also a well-recognised contributor to hair loss in younger women.
Genetics is arguably the strongest predictor of androgenetic alopecia in both sexes. If your parents or grandparents experienced significant hair thinning, your own risk is substantially elevated. Genome-wide association studies have identified numerous genetic loci linked to pattern hair loss, many of which are located on the X chromosome — which is why the condition has historically been associated with inheritance from the maternal side. However, more recent research confirms that genes from both parents contribute to risk.
In men, genetic susceptibility determines how sensitive hair follicles are to DHT. Two men may have identical testosterone and DHT levels, yet one develops extensive baldness while the other retains a full head of hair — the difference lies in the genetic coding of their androgen receptors and the local enzyme activity within their scalp follicles.
For women, the genetic component is equally important but less well characterised. Family history of hair loss on either side increases the risk, and the likelihood rises with age. Harvard Health notes that the risk of female pattern hair loss is "higher for women with a history of hair loss on either side of the family." However, because FPHL may have a more complex, multifactorial aetiology, genetic predisposition alone does not determine outcome — environmental and hormonal factors interact with the genetic blueprint to determine the severity and timing of hair loss. For a more detailed look at concerns specific to women, our female hair loss page provides further guidance.
Nutritional deficiencies are among the most modifiable drivers of hair loss, and they disproportionately affect women. Iron deficiency — even in the absence of frank anaemia — is one of the most common causes of diffuse hair shedding in women. The hair follicle is one of the most metabolically active structures in the body, and it is highly sensitive to reduced nutrient supply. Low ferritin (stored iron) levels have been repeatedly associated with telogen effluvium, a form of hair loss characterised by excessive shedding.
Other nutrients critical to healthy hair growth include zinc, biotin, vitamin D, and essential fatty acids. Severe protein restriction, as seen in crash diets or eating disorders, can also precipitate significant hair loss within a few months. Men are not immune to nutritional hair loss either, though it is less frequently the primary cause in male presentations due to the overwhelming influence of androgenetic factors.
Both hypothyroidism and hyperthyroidism can cause diffuse hair loss. Thyroid hormones play a direct role in hair follicle cycling, and imbalances — even subclinical ones — may slow growth or push a disproportionate number of follicles into the telogen (resting and shedding) phase. This is a particularly important consideration in women, who are far more likely to develop thyroid disease than men.
Insulin resistance and metabolic syndrome have also been linked to hair loss, partly through their effects on androgen metabolism. In women with PCOS, for instance, insulin resistance drives ovarian androgen production, which in turn contributes to follicular miniaturisation. Addressing the metabolic root cause can, in some cases, improve hair outcomes.
Telogen effluvium is a reactive form of hair loss triggered by a physiological or emotional stressor. Common triggers include major surgery, severe illness, high fever, significant weight loss, emotional trauma, and childbirth. The mechanism involves a premature shift of hair follicles from the active growth phase (anagen) into the resting phase (telogen), resulting in noticeable shedding typically two to three months after the triggering event.
The good news is that telogen effluvium is usually self-limiting — once the stressor is resolved, the hair cycle normalises and regrowth occurs over six to twelve months. However, chronic or repeated stressors can lead to chronic telogen effluvium, which is more challenging to manage and may require specialist input.
Lifestyle factors are often underestimated in their contribution to hair health. Smoking impairs microcirculation to the scalp and generates oxidative stress, both of which can accelerate follicular ageing. Excessive alcohol consumption may contribute to nutritional depletion and hormonal disruption. Environmental pollutants, UV radiation, and harsh chemical hair treatments can also damage the hair shaft and follicle over time.
Sleep deprivation and chronic psychological stress elevate cortisol levels, which can disrupt the hair growth cycle and exacerbate existing androgenetic alopecia. While these factors alone rarely cause significant baldness, they can meaningfully worsen hair loss driven by other mechanisms, making lifestyle optimisation an important part of any comprehensive treatment plan.
Alopecia areata is a distinct autoimmune condition in which the body's immune system attacks the hair follicles, causing patchy hair loss that can occur anywhere on the body. Unlike androgenetic alopecia, it is not driven by hormones or genetics in the traditional sense, although genetic susceptibility to autoimmune disease plays a role. It affects both men and women equally and can onset at any age, though it often first appears in childhood or early adulthood.
Other autoimmune and inflammatory conditions — including lupus, dermatomyositis, and lichen planopilaris — can cause scarring alopecia, where the follicles are permanently destroyed. Early diagnosis and treatment are critical in these cases to prevent irreversible loss.
A number of commonly prescribed medications can trigger hair loss as a side effect. The most well-known example is chemotherapy, which targets rapidly dividing cells and causes anagen effluvium — a sudden, widespread loss of actively growing hairs. However, many other medications can cause a more gradual, telogen effluvium-type shedding. These include:
If you suspect a medication may be contributing to your hair loss, it is important to discuss this with your doctor rather than stopping the medication independently. In many cases, an alternative drug or dose adjustment can resolve the issue.
It is worth acknowledging that some degree of hair thinning is a normal part of ageing. Hair growth naturally slows with age, and the proportion of follicles in the resting phase increases. Individual hair strands may also become finer in diameter. This process, known as senescent alopecia, is distinct from androgenetic alopecia and occurs independently of hormonal factors.
In men, age-related thinning typically compounds the effects of DHT-driven loss, making the overall presentation more pronounced. In women, the decline in oestrogen around menopause accelerates thinning, and many women first notice significant hair loss during their late forties or fifties. Understanding that age is a contributing factor — but not an immutable one — is important, because many of the co-existing drivers (nutrition, stress, medication) remain modifiable regardless of age.
For men experiencing hair changes alongside other symptoms such as fatigue or reduced libido, it may be worth exploring whether testosterone replacement therapy (TRT) is appropriate, as testosterone levels naturally decline with age and this can affect overall wellbeing — though it is worth noting that TRT can in some cases worsen androgenetic hair loss, making specialist guidance essential.
Yes. Androgenetic alopecia has a strong genetic component in both sexes. Research shows that genes from both the maternal and paternal sides contribute to risk. If you have close relatives who experienced significant thinning or baldness, your own risk is elevated. However, genetics interacts with hormonal, nutritional, and environmental factors, so family history does not guarantee the same outcome.
Stress-related hair loss (telogen effluvium) is typically temporary. Once the underlying stressor is resolved, most people experience full regrowth within six to twelve months. However, chronic, unresolved stress can lead to prolonged shedding, and in individuals already predisposed to androgenetic alopecia, stress can accelerate the progression of permanent thinning.
The pattern differs largely because of hormonal and receptor-level differences. Men tend to lose hair in a predictable pattern — receding temples and crown thinning — driven primarily by DHT. Women more commonly experience diffuse thinning across the top of the scalp while retaining their frontal hairline. The aetiology in women is often more multifactorial, involving hormonal fluctuations, nutritional deficiencies, and stress alongside any androgenic influence.
Absolutely. Hair follicles are among the most metabolically active cells in the body and require a steady supply of iron, zinc, biotin, vitamin D, protein, and essential fatty acids. Deficiencies in any of these can trigger or worsen hair shedding. Iron deficiency is a particularly common and under-recognised cause of hair loss in women.
You should seek medical advice if you notice sudden or patchy hair loss, significant shedding that persists for more than three months, hair loss accompanied by scalp symptoms (itching, burning, or scarring), or thinning that is causing you distress. Early intervention generally leads to better outcomes, as many forms of hair loss respond more effectively to treatment when addressed promptly.
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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