Understanding Hair Thinning and Hair Loss in Women

As a certified practising nutritionist, I frequently encounter women in their 40s and 50s seeking guidance on hair thinning, reduced volume, and overall diminished hair quality. These concerns often emerge during a transitional phase of life, where hormonal shifts, lifestyle factors, and underlying health issues intersect. Hair growth is a complex process influenced by the hair follicle cycle, which includes growth (anagen), transition (catagen), and resting (telogen) phases. Disruptions in this cycle can lead to noticeable changes, such as diffuse shedding or finer strands. In this article, I will explore evidence-based factors that can impact hair growth in women, with a particular focus on perimenopause, its effects on thyroid health, and how thyroid function ties into hair quality. Drawing from current scientific research, I’ll cover hormonal, nutritional, stress-related, medication-induced, and genetic influences.

Hormonal Changes During Perimenopause and Its Impact on Hair

Perimenopause, the transitional period leading to menopause typically starting in the mid-40s, brings fluctuating hormone levels that can profoundly affect hair. Oestrogen and progesterone levels decline erratically, while androgens like testosterone may become relatively more dominant. Oestrogen plays a protective role in hair health by prolonging the anagen phase, promoting thicker growth and maintaining follicle vitality. As oestrogen drops, hair follicles may shrink, leading to thinner, shorter hairs and increased shedding. Research indicates that this hormonal imbalance contributes to female pattern hair loss (FPHL), characterised by diffuse thinning over the crown and widening part lines (Rinaldi et al., 2023). Women in perimenopause often report not just thinning but also changes in texture, such as drier or more brittle strands, due to reduced sebaceous gland activity.

Stress exacerbates these changes; during perimenopause, heightened stress can trigger telogen effluvium, where more follicles enter the resting phase prematurely, resulting in excessive shedding months later. Hormonal fluctuations also influence other systems, including the thyroid, which we'll discuss next. Not all women experience severe hair loss—genetics, diet, and overall health modulate the severity, but studies show a higher prevalence of alopecia in postmenopausal women compared to premenopausal ones, often linked to lower oestrogen and higher androgen levels (Rinaldi et al., 2023). Management strategies include hormone replacement therapy (HRT) under medical supervision, which may stabilise oestrogen levels and slow thinning, though evidence varies by individual response.

The Interplay Between Perimenopause, Thyroid Health, and Hair Loss

Thyroid health is intricately linked to perimenopause, as hormonal shifts can disrupt thyroid function, leading to conditions such as hypothyroidism or hyperthyroidism. During perimenopause, declining oestrogen may contribute to thyroid imbalances, with studies noting that 12-20% of women over 60 have underactive thyroids, often overlapping with menopausal symptoms (Hussein et al., 2023). Thyroid hormones (THs), such as thyroxine (T4) and triiodothyronine (T3), regulate metabolism, cell growth, and differentiation, directly influencing hair follicle cycling. THs promote the anagen phase by stimulating proliferation in the hair matrix and modulating keratin expression.

In hypothyroidism, common in midlife women, slowed metabolism leads to coarse, dry, brittle hair and diffuse shedding, sometimes with loss of the outer third of eyebrows. This occurs because low TH levels delay the transition from telogen to anagen, prolonging the resting phase. Hyperthyroidism, less common but possible, causes fine, silky hair and widespread shedding due to accelerated cycles and oxidative stress from reactive oxygen species. Autoimmune thyroid diseases, like Hashimoto's thyroiditis, are prevalent in women and associated with alopecia areata, patchy hair loss driven by immune attacks on follicles (Hussein et al., 2023). Approximately 33% of hypothyroid and 50% of hyperthyroid individuals experience hair loss, often reversible with treatment like levothyroxine, though regrowth may take months and differ in texture.

Perimenopause amplifies these issues; oestrogen decline can mimic or worsen thyroid symptoms, leading to misdiagnosis. Blood tests for TSH, T4, and antibodies are crucial for accurate assessment. Lifestyle factors, such as iodine intake from diet, support thyroid function, but supplementation should be monitored to avoid excess.

Autoimmune Hair Loss: Alopecia Areata and Its Links to Hormonal Changes

Alopecia areata (AA) is a common autoimmune condition affecting up to 2% of the population, characterised by sudden, patchy hair loss due to T-cell mediated attacks on hair follicles, interrupting the growth phase and causing smooth, round bald spots. While it can occur at any age, new onset or flares in midlife women often coincide with perimenopause, where hormonal fluctuations play a potential triggering role. Oestrogen and progesterone modulate immune function, and their erratic decline can disrupt immune tolerance, promoting inflammation around follicles. Emerging research highlights that shifts in sex hormones like oestrogen and testosterone, alongside stress hormones such as cortisol, can exacerbate autoimmune responses, leading to AA in genetically susceptible individuals (Almohammadi, 2024). Thyroid autoimmunity, already linked to perimenopause, further increases risk, with studies showing higher AA prevalence in women with Hashimoto's.

Regarding hormone replacement therapy (HRT), which is frequently prescribed to alleviate perimenopausal symptoms and support hair health, the evidence is nuanced. While HRT generally stabilises oestrogen levels and may improve diffuse thinning, emerging case reports and clinical observations suggest it can rarely trigger or worsen AA through sudden hormonal shifts that dysregulate the immune system, particularly if formulations include androgenic progestogens (Maleki et al., 2025). For instance, abrupt oestrogen surges or imbalances may provoke autoimmune flares in predisposed women, though large-scale studies are limited and most data indicate benefits for overall hair quality. Women with a family history of autoimmunity should monitor for patches post-HRT initiation and consult dermatologists early. Treatments such as topical corticosteroids or JAK inhibitors offer hope for regrowth, emphasising the need for multidisciplinary care.

Nutritional Deficiencies: Building Blocks for Healthy Hair

Nutrition is foundational to hair growth, as follicles require a steady supply of vitamins, minerals, and proteins. In women aged 40-50, dietary changes, malabsorption, or restrictive eating can lead to deficiencies exacerbating hair issues. Iron deficiency, prevalent due to menstrual blood loss or vegetarian diets, impairs oxygen delivery to follicles, causing telogen effluvium. Studies link low ferritin (iron storage) to chronic diffuse shedding, with mechanisms involving disrupted DNA synthesis in rapidly dividing matrix cells (Guo & Katta, 2017).

Zinc deficiency affects protein synthesis and is lower in those with AA or pattern hair loss, leading to brittle strands. Vitamin D insufficiency, common in midlife due to reduced sun exposure or obesity, correlates with FPHL severity, as it supports follicle differentiation. Biotin aids in keratin production; deficiencies from gut issues or antibiotics cause alopecia. Essential fatty acids from fish and nuts modulate inflammation and androgen effects, while protein malnutrition thins hair by starving follicles (Guo & Katta, 2017). Excess vitamin A from supplements, however, can trigger loss.

As a certified practising nutritionist (CPN), I recommend a balanced diet rich in leafy greens, lean proteins, nuts, and omega-3s. For deficiencies, targeted supplementation may be required, for example, bioavailable iron with vitamin C to enhance absorption can help, but only after testing, as over-supplementation risks toxicity.

The Role of Stress in Disrupting Hair Cycles

Chronic stress is a silent culprit in hair loss, particularly for busy women going through perimenopause, juggling careers and family. Stress elevates cortisol, which inhibits hair regrowth by acting on dermal papilla cells, preventing secretion of growth-activating molecules such as GAS6. Animal studies show prolonged stress keeps follicles in extended telogen, leading to thinning (Choi et al., 2021, as cited in NIH research). In women, this manifests as telogen effluvium, with shedding peaking 3-6 months post-stressor.

Perimenopause heightens vulnerability, as hormonal instability amplifies stress responses. Management includes mindfulness, yoga, breathwork, and adequate sleep, which can restore cycles without medication.

Medications That May Contribute to Hair Thinning

Certain medications can induce hair loss. Chemotherapy causes anagen effluvium by damaging growing follicles, leading to rapid shedding. Antidepressants, blood thinners, and retinoids disrupt cycles, while hormone therapies such as birth control may trigger telogen effluvium in susceptible women. Always consult providers about alternatives if loss occurs.

Genetic Factors: The Inherited Blueprint for Hair Health

Genetics play a pivotal role in FPHL, affecting up to 40% of women by age 50. Unlike male pattern baldness, FPHL's genetic basis is polygenic and less understood, involving variants in genes such as HSD3B1 (androgen metabolism) and VDR (vitamin D receptor). Family history, especially maternal, predicts early onset, with SNPs in CYP19A1 and ESR2 influencing hormone pathways (Ho et al., 2023). Genetics interact with hormones and environment, explaining variable expression.

Hair thinning in women 40-50 often stems from intertwined factors including perimenopausal hormones, thyroid imbalances, nutrition gaps, stress, medications, and genetics. Addressing these through lifestyle, diet, and medical interventions can improve outcomes. As a CPN, I emphasise nutrient-dense eating and stress management. With evidence-based approaches, many women regain confidence in their hair. If you would like support, book a consultation here, today.

References

Guo, E. L., & Katta, R. (2017). Diet and hair loss: Effects of nutrient deficiency and supplement use. Dermatology Practical & Conceptual, 7(1), 1–10. https://doi.org/10.5826/dpc.0701a01

Ho, C.-Y., Chen, J. Y.-F., Hsu, W.-L., Yu, S., Chen, W.-C., Chiu, S.-H., Yang, H.-R., Lin, S.-Y., & Wu, C.-Y. (2023). Female pattern hair loss: An overview with focus on the genetics. Genes, 14(7), 1326. https://doi.org/10.3390/genes14071326

Hussein, R. S., Atia, T., & Bin Dayel, S. (2023). Impact of thyroid dysfunction on hair disorders. Cureus, 15(8), e43266. https://doi.org/10.7759/cureus.43266

Rinaldi, F., Trink, A., Mondadori, G., Giuliani, G., & Pinto, D. (2023). The menopausal transition: Is the hair follicle “going through menopause”? Biomedicines, 11(11), 3041. https://doi.org/10.3390/biomedicines11113041