What side of the family does hair loss come from? It is a question many people ask when they notice their hair thinning, often glancing at a grandfather's photograph for clues. The popular belief that baldness is inherited solely from the mother's side is a persistent myth — the reality is considerably more nuanced. Hair loss, particularly androgenetic alopecia (pattern baldness), is a polygenic condition influenced by hundreds of genetic variants inherited from both parents. Hormonal, nutritional, and lifestyle factors also play important roles. This article explains the genetics of hair loss, other contributing causes, when to seek medical advice, and the treatment options available in the UK.

How Genetics Influence Hair Loss

Hair loss is a polygenic trait influenced by hundreds of genetic variants across multiple chromosomes, affecting follicle sensitivity to DHT; no single gene or parent determines risk.

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Hair loss — particularly the most common form known as androgenetic alopecia (pattern baldness) — has a strong genetic basis. Research consistently shows that inherited factors play a significant role in determining whether a person will experience hair thinning or baldness during their lifetime. However, the genetics of hair loss are considerably more complex than many people assume.

Androgenetic alopecia is what scientists call a polygenic trait, meaning it is influenced by multiple genes rather than a single inherited gene. Large-scale genome-wide association studies (GWAS), including research using the UK Biobank cohort published in PLOS Genetics, have identified hundreds of genetic variants associated with pattern hair loss, spread across many chromosomes. These genes affect how sensitive hair follicles are to dihydrotestosterone (DHT), a hormone derived from testosterone. A particularly well-studied gene is the androgen receptor (AR) gene, located on the X chromosome — this underpins the commonly cited (but incomplete) idea that hair loss is inherited from the mother's side. When follicles are genetically predisposed to DHT sensitivity, they gradually shrink over time — a process called follicular miniaturisation — leading to progressively finer, shorter hairs and, eventually, no hair growth at all.

Key points about the genetics of hair loss include:

• Multiple genes across different chromosomes are involved

• Genes can be inherited from both parents

• The condition affects both men and women, though patterns differ

• Genetic predisposition does not guarantee hair loss will occur — environmental and hormonal factors also play a role

Because so many genes contribute to androgenetic alopecia, predicting hair loss based solely on family history is unreliable. A person may inherit a combination of genes from both sides of the family that either increases or reduces their overall risk. Understanding this complexity is important for setting realistic expectations about personal hair loss risk.

Which Parent Passes Down Hair Loss Genes?

Hair loss genes are inherited from both parents — the maternal X chromosome carries the AR gene, but over 200 additional variants on autosomes confirm a significant paternal contribution.

A widely held belief is that hair loss is inherited exclusively from the mother's side of the family — specifically through the maternal grandfather. This idea stems from the fact that the androgen receptor (AR) gene, located on the X chromosome, is indeed passed from mother to son. Since men inherit their X chromosome from their mother, this gene does have a maternal link.

However, this is only part of the picture. GWAS research, including a large study using UK Biobank data published in PLOS Genetics (2017), identified over 200 genetic variants linked to male pattern hair loss, distributed across both the X chromosome and multiple autosomes (non-sex chromosomes) inherited equally from both parents. The same research confirmed that men with bald fathers were significantly more likely to experience hair loss themselves, demonstrating a clear paternal contribution as well.

In practical terms, this means:

• Hair loss genes can be inherited from either or both parents

• Looking at your maternal grandfather gives some indication of risk, but is not definitive

• A bald father also meaningfully increases your likelihood of hair loss

• Women can inherit hair loss genes too, often presenting as diffuse thinning rather than a receding hairline

Family history can improve risk estimation but cannot reliably predict outcomes for any individual. To directly address the question of what side of the family hair loss comes from — the honest answer is both sides. Focusing solely on one parent's family history may give a false sense of security or unnecessary concern. A balanced look at hair loss patterns across both maternal and paternal relatives provides a more accurate, though still imperfect, picture of personal risk.

Other Factors That Contribute to Hair Loss

Hormonal conditions, nutritional deficiencies, stress, medications, and autoimmune disorders can all trigger or accelerate hair loss independently of genetic predisposition.

While genetics lay the foundation, hair loss is rarely caused by inherited factors alone. A range of medical, hormonal, nutritional, and lifestyle influences can trigger or accelerate hair shedding — and in many cases, these causes are entirely reversible once identified and addressed.

Hormonal changes are among the most common non-genetic contributors. Conditions such as polycystic ovary syndrome (PCOS), thyroid disorders (both hypothyroidism and hyperthyroidism), and the hormonal shifts following pregnancy or menopause can all lead to significant hair thinning. The NHS recognises these as important and treatable causes of hair loss in women.

Nutritional deficiencies — particularly low levels of iron and ferritin — are associated with diffuse hair shedding. Evidence for the role of vitamin D, zinc, and biotin in hair loss is less consistent, and testing or supplementation for these is generally only appropriate where a deficiency has been confirmed by a clinician. This type of hair loss, known as telogen effluvium, occurs when a large number of hairs simultaneously enter the resting (telogen) phase and subsequently shed. It is often triggered by:

• Significant physical or emotional stress

• Crash dieting or rapid weight loss

• Major illness, surgery, or high fever

• Certain medications, including anticoagulants, retinoids, and some antidepressants (this list is not exhaustive; consult the medication's patient information leaflet or your pharmacist)

Important note on biotin supplements: If you are taking biotin (vitamin B7) supplements, you must inform your GP or nurse before having blood tests. The MHRA has warned that biotin can interfere with a range of laboratory immunoassays, potentially causing falsely abnormal results for thyroid function, hormone levels, and other tests.

Autoimmune conditions such as alopecia areata — where the immune system mistakenly attacks hair follicles — can cause patchy hair loss and are unrelated to the androgenetic pathway. Scalp conditions including seborrhoeic dermatitis, psoriasis, and fungal infections (tinea capitis) may also contribute to hair loss if left untreated.

Traction alopecia — hair loss caused by prolonged tension on the hair from tight hairstyles such as braids, ponytails, or extensions — is an increasingly recognised and preventable cause. Trichotillomania, a condition involving compulsive hair pulling, can also result in patchy hair loss and may benefit from psychological support.

It is worth noting that stress and poor sleep have been increasingly linked to hair shedding, though lifestyle factors alone are not established as a cause of permanent pattern baldness. Addressing underlying health conditions often results in meaningful hair regrowth.

When to Seek Medical Advice About Hair Loss

See your GP promptly if hair loss is sudden, patchy, accompanied by scalp changes, or associated with other symptoms such as fatigue or irregular periods, as underlying causes need ruling out.

Many people experience some degree of hair shedding throughout their lives, and losing between 50 and 100 hairs per day is considered entirely normal. However, certain patterns of hair loss warrant prompt medical attention to rule out underlying conditions and begin appropriate management.

You should contact your GP if you notice any of the following:

• Sudden or rapid hair loss over a short period

• Patchy bald spots on the scalp, beard, or eyebrows

• Hair loss accompanied by scalp redness, itching, scaling, or pain

• Thinning hair alongside other symptoms such as fatigue, weight changes, or irregular periods

• Hair loss following a new medication

• Significant psychological distress related to hair loss

Seek urgent or prompt GP review if you notice signs that may suggest scarring alopecia — a group of conditions that can permanently destroy hair follicles. Warning signs include a shiny or smooth scalp, loss of visible follicular openings, or skin changes at the margins of hair loss. Early referral to a dermatologist is important to prevent irreversible hair loss. Similarly, children with suspected tinea capitis (scalp ringworm) should be assessed promptly, as this condition requires systemic antifungal treatment and can spread to others.

Your GP will typically begin with a thorough history and examination, followed by blood tests to check for common underlying causes. These may include:

• Full blood count (to check for anaemia)

• Thyroid function tests

• Serum ferritin and iron studies

• Hormone profile (including androgens in women where PCOS is suspected)

• Vitamin D levels (where clinically indicated)

In cases where the diagnosis is unclear or hair loss is severe, your GP may refer you to a dermatologist or, where appropriate, an endocrinologist. Guidance from the Primary Care Dermatology Society (PCDS) and NICE Clinical Knowledge Summary (CKS) on alopecia areata support a structured approach to investigating hair loss in primary care, ensuring that reversible causes are identified before attributing hair loss purely to genetics. Early assessment is particularly important for women, as female-pattern hair loss is often underdiagnosed and undertreated. Seeking advice sooner rather than later generally leads to better outcomes.

Treatment Options for Hair Loss

Minoxidil (over the counter) and finasteride (prescription-only for men) are the most evidence-based treatments for pattern baldness; treating an underlying medical cause often restores hair naturally.

Treatment for hair loss depends largely on the underlying cause. Where a medical condition such as thyroid disease, iron deficiency anaemia, or PCOS is identified, treating that condition often leads to natural hair regrowth without the need for specific hair loss therapies.

For androgenetic alopecia (pattern baldness), it is important to note that in England, treatments for pattern hair loss are not routinely available on the NHS and are typically obtained over the counter or via a private prescription. The two most evidence-based treatments are:

• Minoxidil (available over the counter as a topical solution or foam, Pharmacy medicine): Originally developed as a blood pressure medication, minoxidil prolongs the anagen (growth) phase of the hair cycle and increases follicular size. It is available for both men and women and requires ongoing use to maintain results. Minoxidil should not be used during pregnancy or breastfeeding; age restrictions and full safety information are detailed in the product's Summary of Product Characteristics (SmPC), available on the Electronic Medicines Compendium (EMC). Consult a pharmacist or GP if you are unsure whether it is suitable for you.

• Finasteride (prescription-only medicine, for men): This oral medication works by inhibiting the enzyme 5-alpha reductase, thereby reducing DHT levels and slowing follicular miniaturisation. It is not recommended for women of childbearing age due to risks of foetal harm. Important MHRA safety information: Finasteride has been associated with sexual dysfunction (including decreased libido, erectile dysfunction, and ejaculation disorders) and psychiatric effects (including depression, anxiety, and, rarely, suicidal thoughts). These effects may persist after stopping the medication. Patients should be given a patient alert card when starting finasteride and should seek medical advice promptly if they experience mood changes or sexual side effects. Full prescribing information is available in the finasteride SmPC on the EMC.

For alopecia areata, treatments available through NHS dermatology services may include corticosteroid injections, topical immunotherapy, or referral to a specialist. NICE CKS and the British Association of Dermatologists (BAD) provide guidance on managing this condition. JAK inhibitors represent a newer treatment class for severe alopecia areata: ritlecitinib (Litfulo) has received MHRA marketing authorisation for severe alopecia areata in adults and adolescents aged 12 and over, and baricitinib (Olumiant) also holds a licence for this indication. Access to these medicines in the NHS is subject to specialist assessment and local or national commissioning decisions; your dermatologist can advise on current availability.

Beyond medical treatment, the psychological impact of hair loss is well recognised. Referral to talking therapies or support groups may be appropriate, particularly where hair loss is causing significant distress. Organisations such as Alopecia UK offer peer support and practical guidance. Wigs and hairpieces may be available on NHS prescription for certain conditions, including alopecia areata and hair loss resulting from chemotherapy — your GP or specialist can advise on eligibility.

Reporting side effects: If you experience a suspected side effect from any hair loss treatment, you can report it to the MHRA via the Yellow Card Scheme at yellowcard.mhra.gov.uk.

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