Author note: This article is written by Dr Iaisha Ali, lead author of the landmark 2011 study on postmenopausal hair changes published in the British Journal of Dermatology (Ali I & Wojnarowska F, 2011). That work — the first comprehensive population-based study of its kind — forms a key evidence base for the menopausal section of this article.
Introduction
Hair loss is one of the most distressing and frequently overlooked manifestations of thyroid dysfunction. While fatigue, weight gain, and cold intolerance are the most commonly recognised symptoms of an underactive thyroid (hypothyroidism), a significant number of patients present first — and sometimes exclusively — with diffuse thinning of the scalp. Understanding the bidirectional relationship between thyroid hormones and the hair follicle cycle is essential for clinicians and patients alike, particularly given the rising burden of hypothyroidism in the United Kingdom.
Epidemiology: The UK Burden of Hypothyroidism
Hypothyroidism is among the most common endocrine disorders in the United Kingdom and its prevalence is rising. Data examining NHS and Office of National Statistics records across all 237 health areas found that the prevalence of treated hypothyroidism increased from 2.3% (approximately 1.4 million people) in 2005 to 3.5% (2.2 million) by 2014, with projections estimating a further rise to 4.2% (2.9 million) by 2025 (Leese et al., Thyroid, 2019). This represents one of the steepest increases of any chronic endocrine condition in the UK over the last two decades.
The condition is strongly sex-linked: hypothyroidism is seen ten times more often in women than in men, with a UK female-to-male ratio of approximately 6:1. The incidence of clinical (overt) hypothyroidism has been estimated at 40 per 10,000 women per year compared with just 6 per 10,000 men per year (AAFP, 2015). The overall prevalence of clinically overt hypothyroidism sits at approximately 1–2% of the general UK population, though subclinical hypothyroidism — where TSH is elevated but free T4 remains within range — is found in 8–10% of the population, increasing substantially with age (Thyroid UK).
A UK survey found that approximately 7.5% of women and 2.8% of men have elevated serum TSH levels when screened, suggesting that a large proportion of cases remain undiagnosed or untreated (Hussein et al., PMC, 2019). There is significant geographical variation within the UK: London reports the lowest prevalence of treated hypothyroidism (1.4%), while the Western Isles of Scotland records the highest (6.3%), a pattern partially explained by iodine availability, ethnicity, and environmental factors.
Of particular clinical relevance is the relationship between hypothyroidism and the menopausal transition. The incidence of thyroid disease — including hypothyroidism — is highest in postmenopausal women, and symptoms frequently overlap, leading to diagnostic delays. Hypothyroidism is most commonly diagnosed in women aged 40–50 years, often coinciding with perimenopause. Many women find it difficult to distinguish between hair change during menopause and a pathological thyroid condition.
The Thyroid Gland and the Hair Follicle: Biological Mechanisms
The thyroid gland produces two principal hormones: thyroxine (T4, the prohormone) and triiodothyronine (T3, the biologically active form). These regulate metabolism, cell growth, differentiation, and thermogenesis throughout the body. The hair follicle is a highly metabolically active structure and one of the most sensitive target organs for thyroid hormones.
Thyroid hormone receptors are expressed directly within the hair follicle, particularly in the dermal papilla — the mesenchymal core of the follicle that governs hair cycling. T3 and T4 play a direct role in regulating follicular activity at the root. When hormone levels become insufficient, hair follicles may enter the telogen (resting) phase prematurely, remain there longer than normal, and fail to transition back into the anagen (growth) phase.
The Hair Growth Cycle: Disrupted by Hypothyroidism
Normal hair cycling consists of four phases:
- Anagen – active growth (lasting 2–7 years on the scalp)
- Catagen – regression (2–3 weeks)
- Telogen – resting (approximately 3 months)
- Exogen – shedding
In states of adequate thyroid function, the vast majority of scalp hairs (~85–90%) are in the anagen phase at any given time. In hypothyroidism, this balance is disrupted. Hypothyroidism inhibits cell division in the epidermis and skin appendages, resulting in an increased proportion of hairs in the telogen (resting) phase. The prolonged telogen phase eventually results in excessive shedding — the hallmark of hair shedding or hair loss (telogen effluvium). (Hussein et al., Cureus, 2023).
A retrospective study of 500 female patients with telogen effluvium, examining thyroid function over a decade (2012–2022), found that the hypothyroid group had a significantly higher mean severity of alopecia (SALT) score than both euthyroid and hyperthyroid groups, with a higher proportion of patients experiencing severe hair loss. These findings support the hypothesis that hypothyroidism is a common and frequently underestimated cause of telogen effluvium (published in Medicine, 2024).
Importantly, hypothyroid hair loss typically presents as diffuse thinning across the scalp rather than a localised patch. A classic additional clinical sign is thinning or loss of the outer third of the eyebrows — known as the Sign of Hertoghe — which, while not pathognomonic, is a useful clinical pointer. Hair quality also deteriorates: thyroid hormones regulate sebum production and the structural integrity of the hair cuticle. Without adequate hormonal support, hair becomes dry, brittle, and coarse before visible shedding begins.
It is also important to note that hair loss due to thyroid disease typically becomes apparent several months after the onset of thyroid dysfunction, given the length of the hair growth cycle. This lag frequently confuses both patients and clinicians.
The Menopausal Overlap: A Compounding Factor
The convergence of hypothyroidism with menopause represents a particularly significant clinical challenge. In the first comprehensive population-based study of its kind, the author of this article — Ali and Wojnarowska (2011) — examined subjective hair changes across the scalp, face, and body in postmenopausal women of northern European origin aged 45 years or over, published in the British Journal of Dermatology (164(3):508–513). Crucially, women with a history of thyroid disease were excluded from the study, allowing the authors to characterise hair changes attributable specifically to the menopausal transition rather than thyroid dysfunction.
Their findings revealed two distinct patterns: diffuse generalised scalp hair loss, reported by 26% of women, which was significantly correlated with body hair loss and increasing age; and frontal hair loss, reported by 9% of women, which was associated with higher facial hair scores and relatively younger age. Facial hair gain — particularly at the chin — was reported by 39% of participants. These two patterns likely reflect different underlying pathophysiological mechanisms, with diffuse hair loss representing progressive androgen-related follicular change with ageing, and frontal loss reflecting an earlier androgenic hormonal shift. The study underscores the importance of distinguishing physiological postmenopausal hair change from pathological causes — including hypothyroidism — and provides a critical reference framework for clinicians assessing hair loss in this age group.
The broader hormonal milieu of the menopausal transition — characterised by declining oestrogen and progesterone and a relative increase in androgens — directly impacts the hair follicle, which is an oestrogen-sensitive tissue. These hormonal fluctuations lead to decreased hair density, reduced hair calibre, and changes in hair texture.
The broader literature strongly supports this intersection. A 2025 review in Maturitas (Gupta et al.) notes that female-pattern hair loss, telogen effluvium, and frontal fibrosing alopecia all occur with higher frequency in postmenopausal women. Oestrogen acts as a “hair-friendly hormone,” prolonging the anagen phase and protecting follicles against androgen-mediated miniaturisation. When oestrogen declines, these protective effects are lost — and if hypothyroidism co-exists (as it commonly does in this demographic), the impact on hair is compounded by two independent but synergistic hormonal mechanisms.
A 2023 paper in Biomedicines (Rinaldi et al.) further explored the concept of the hair follicle itself “going through menopause” — proposing that hormonal fluctuations and reduced metabolic efficiency during the menopausal transition directly alter follicular energy metabolism and reduce blood flow to the follicular unit, impairing nutrient delivery. This has important implications for nutritional management (see below).
Given the significant symptomatic overlap between hypothyroidism and menopause — including fatigue, mood changes, weight gain, dry skin, and hair loss — clinicians must maintain a low threshold for thyroid function testing in perimenopausal and postmenopausal women presenting with hair concerns.
Diagnosis: Laboratory Testing for Hypothyroidism
If you suspect a thyroid disease hair issue, comprehensive testing is required:
TSH (Thyroid-stimulating hormone) is the primary and most sensitive first-line test for diagnosing hypothyroidism. Produced by the anterior pituitary, TSH stimulates the thyroid to produce T4 and T3. In primary hypothyroidism, reduced thyroid output results in a compensatory rise in TSH. UK guidelines from the Association of Clinical Biochemistry, the British Thyroid Association, and the British Thyroid Foundation recommend TSH as the frontline investigation, with FT4 automatically reflexed by the laboratory if TSH is abnormal.
A TSH of >10 mU/L combined with a free T4 below the reference range is consistent with overt primary hypothyroidism and warrants treatment.
Free Thyroxine (FT4)
Free T4 measures the amount of unbound (bioavailable) thyroxine circulating in the blood. It is essential when:
- TSH is elevated, to confirm the degree of thyroid failure
- Secondary (central) hypothyroidism is suspected (where TSH may be normal or only mildly raised despite low FT4)
- The patient is on thyroid hormone replacement therapy
Free Triiodothyronine (FT3)
FT3 is rarely requested as a first-line test in the UK context of suspected hypothyroidism, and its utility in diagnosis is limited due to high variability. However, it may be helpful in evaluating suspected secondary hypothyroidism, in patients on combined T3/T4 therapy, and in cases where T3 toxicosis is a differential diagnosis.
Thyroid Peroxidase Antibodies (TPOAb)
Used to identify Hashimoto’s thyroiditis. Research suggests a higher prevalence of these antibodies in patients with alopecia areata. Studies have found a significantly higher prevalence of antithyroid antibodies (25.7%) in patients with alopecia compared to healthy controls (3.3%), highlighting the shared autoimmune pathogenesis of certain hair loss conditions and thyroid disease (Kasumagić-Halilović et al., as cited in MDPI, 2023). Although anti-TPO testing seldom changes the initial treatment (levothyroxine), it identifies patients at higher risk of progression from subclinical to overt hypothyroidism, and those with potential co-existing alopecia areata.
Subclinical Hypothyroidism
In subclinical hypothyroidism, TSH is elevated but FT4 remains within the reference range, and symptoms may be present or absent. This is found in 8–10% of the UK population and is more common in women and older individuals. Hair loss may be a presenting symptom. Current NHS practice is to monitor rather than treat subclinical hypothyroidism in most cases unless the TSH exceeds 10 mU/L, symptoms are significant, or the patient is pregnant.
Practical Note on NHS Testing
In the UK, NHS GPs generally test only TSH as first-line. FT4 is measured reflexively in many, but not all, areas. Testing for FT3 and thyroid antibodies is not routinely undertaken but can be requested when there is clinical reason. Patients undergoing private thyroid screening may access a more comprehensive panel. Clinicians assessing hair loss should ensure thyroid function tests are performed in the appropriate clinical context, alongside other relevant investigations such as ferritin, full blood count, and vitamin D.
Nutritional Factors Contributing to Thyroid-Related Hair Loss
Nutritional deficiencies are both a consequence of hypothyroidism and an independent contributing factor to hair loss. Identifying and addressing these deficiencies alongside thyroid treatment is fundamental to optimising hair recovery.
Iron and Ferritin
Iron is required for the synthesis of thyroid hormones through its role as a cofactor for haem-dependent thyroid peroxidase (TPO), the enzyme responsible for producing T4. When iron stores are depleted, TPO activity is reduced, impairing thyroid hormone production and worsening hypothyroid symptoms. Critically, iron deficiency is independently associated with telogen effluvium even in euthyroid individuals, meaning the two conditions compound one another significantly.
Ferritin (the iron storage protein) is the most sensitive marker of iron status in the context of hair loss. Studies suggest that 25% of women with hypothyroidism experience hair loss partly attributable to low ferritin levels (Avant Medical Group, 2025). Low ferritin is especially prevalent in premenopausal women with heavy menstrual bleeding — a symptom which hypothyroidism itself can exacerbate — and in those following vegetarian or vegan diets. Patients should have both serum ferritin and a full blood count measured; clinicians are advised to request ferritin specifically, as standard iron panels may be normal despite suboptimal stores.
Selenium
Selenium is required for the deiodinase enzymes that convert the inactive T4 into the biologically active T3. Selenium deficiency impairs this conversion, perpetuating a state of functional hypothyroidism even when T4 levels appear adequate. It also plays a role in modulating the autoimmune response in Hashimoto’s thyroiditis: a Cochrane Review (2013) found that selenium supplementation reduced anti-TPO antibody levels by 20–40% in Hashimoto’s patients. Brazil nuts are among the richest dietary sources, with a single nut providing approximately 70–90 mcg.
Zinc
Zinc is required for thyroid hormone synthesis, the function of thyroid hormone receptors, and the production of keratin — the structural protein of the hair shaft. A study published in the Annals of Dermatology (2013) found that zinc deficiency was present in 66.7% of patients presenting with hair loss, underscoring its importance in trichological practice. Dietary sources include pumpkin seeds, oysters, lentils, and chickpeas.
Iodine
Iodine is the essential raw material from which thyroid hormones are constructed: approximately 70–80% of the body’s iodine is concentrated within the thyroid gland. Iodine deficiency can directly cause hypothyroidism and goitre. However, excessive iodine supplementation can paradoxically trigger or worsen thyroid dysfunction, particularly in those with existing autoimmune thyroid disease. Supplementation should only be considered when deficiency is confirmed, and should always be supervised.
Vitamin D
Vitamin D acts as a modulator of immune function and inflammation, and low levels have been associated with increased risk and severity of autoimmune thyroid disorders, including Hashimoto’s thyroiditis. Vitamin D deficiency is highly prevalent in the UK general population — particularly during the autumn and winter months — and is independently associated with hair follicle cycling dysfunction. Public Health England recommends that all adults in the UK consider vitamin D supplementation (10 mcg/day) during autumn and winter.
Biotin (Vitamin B7)
Biotin is widely marketed as a hair growth supplement, and while biotin deficiency can theoretically contribute to hair thinning, clinical deficiency is uncommon. Of greater clinical importance is that biotin supplementation can significantly interfere with thyroid function blood tests, producing falsely abnormal TSH and FT4 results. The MHRA has issued safety guidance on this issue. Patients should be advised to stop biotin supplementation at least 48 hours before thyroid blood tests and should inform their GP and laboratory if they are taking it.
Clinical Implications and Management
The management of hypothyroid-related hair loss centres primarily on adequate thyroid hormone replacement with levothyroxine, targeting a TSH within the normal reference range as per NICE guidance (NG145). Hair regrowth following the commencement of treatment typically begins within several months of achieving euthyroidism, though full restoration may take 6–12 months or longer, depending on the duration of untreated hypothyroidism.
Alongside pharmacological management, clinicians should:
- Assess and correct nutritional deficiencies, particularly ferritin, vitamin D, zinc, and selenium
- Evaluate for co-existing alopecia areata, female-pattern hair loss, or frontal fibrosing alopecia, which may require additional specialist trichological management
- Consider the hormonal context — particularly in perimenopausal and postmenopausal women — and liaise with menopause specialists where appropriate
- Advise patients that thyroid-related hair loss is typically reversible with timely and adequate treatment, provided nutritional status is optimised and concurrent conditions are excluded
As the author’s own landmark population-based study demonstrated (Ali & Wojnarowska, 2011), the subjective experience of hair change following the menopause is highly prevalent and takes distinct clinical forms — and the emotional and psychological burden of hair thinning in women should not be underestimated. Hair loss is deeply connected to identity and wellbeing, and patients benefit significantly from validation, a clear diagnostic framework, and a multidisciplinary approach integrating trichology, endocrinology, and — where relevant — menopause medicine.
Conclusion
Hypothyroidism is a common and rising condition in the UK, disproportionately affecting women — particularly in the perimenopausal and postmenopausal years. Hair loss is a frequently underappreciated manifestation of thyroid dysfunction, mediated through disruption of the hair follicle growth cycle and compounded by nutritional deficiencies that are themselves either caused or exacerbated by hypothyroidism. Diagnosis rests on a stepwise biochemical approach anchored by TSH measurement, with FT4, FT3, and anti-TPO antibodies deployed selectively. Nutritional assessment — particularly of iron/ferritin, selenium, zinc, vitamin D, and iodine — is integral to clinical management. When hypothyroidism coincides with menopause, the effect on hair is compounded, and a holistic, evidence-based approach is essential for effective patient care. If you are experiencing thyroid and hair loss, a multidisciplinary approach at our Harley Street clinic ensures all potential causes — from exercise and skin health to endocrine balance — are considered.
Key References
- Leese GP et al. (2019). Trends, Determinants, and Associations of Treated Hypothyroidism in the United Kingdom, 2005–2014. Thyroid. doi:10.1089/thy.2018.0251
- Thyroid UK. Overview of Hypothyroidism. Available at: thyroiduk.org [Accessed May 2026]
- Hussein RS, Atia T, Bin Dayel S. (2023). Impact of Thyroid Dysfunction on Hair Disorders. Cureus, 15(8):e43266. doi:10.7759/cureus.43266
- Al-Refu K. (2024). Is Thyroid Dysfunction a Common Cause of Telogen Effluvium? Medicine. doi:10.1097/MD.0000000000036706
- Gupta AK et al. (2025). Menopause and Hair Loss in Women: Exploring the Hormonal Transition. Maturitas, 198:108378. doi:10.1016/j.maturitas.2025.108378
- Rinaldi F et al. (2023). The Menopausal Transition: Is the Hair Follicle “Going through Menopause”? Biomedicines, 11(11):3041. doi:10.3390/biomedicines11113041
- Ali I, Wojnarowska F. (2011). Physiological changes in scalp, facial and body hair after the menopause: a cross-sectional population-based study of subjective changes. British Journal of Dermatology, 164(3):508–513. doi:10.1111/j.1365-2133.2010.10156.x
- British Thyroid Association / Association of Clinical Biochemistry (2006). UK Guidelines for the Use of Thyroid Function Tests. Available at: baets.org.uk
- NICE (2019). Thyroid Disease: Assessment and Management. Guideline NG145. Available at: nice.org.uk
- Bolt Pharmacy (2026). Vitamins for Thyroid Hair Loss: Nutrients, Supplements and NHS Advice. Available at: boltpharmacy.co.uk
- Study of the Thyroid Profile of Patients with Alopecia. MDPI, 2023. PMC9918246.
- Vincent M, Yogiraj K. (2013). A Descriptive Study of Alopecia Patterns and their Relation to Thyroid Dysfunction. International Journal of Trichology, 5(1):57–60.
