Why Are My Eyebrows Thinning? Common Causes Explained

What does the outer-third pattern mean?

Clinicians often pay close attention to whether eyebrow thinning is most prominent in the outer (lateral) one-third of the brow. This pattern has long been associated with hypothyroidism and is sometimes called the Hertoghe sign or Queen Anne's sign. It is not a definitive diagnostic test on its own — the same pattern can appear with aging, atopic dermatitis, alopecia areata, and other conditions — but it is a useful clue that reliably prompts thyroid evaluation. Thinning that is uniform across the brow, or that affects the inner segment more than the outer, may point toward different causes.

Is thyroid disease the cause?

Both underactive thyroid (hypothyroidism) and overactive thyroid (hyperthyroidism) can disrupt the hair growth cycle and cause diffuse shedding, including at the eyebrows 1Ref 1Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Thyroid dysfunction is common and straightforwardly treated once diagnosed; TSH is the primary screening test2Ref 2Hussein RS, Atia T, Bin Dayel S (2023).Impact of Thyroid Dysfunction on Hair Disorders.Thyroid hormones regulate cell growth and metabolism; both hypothyroidism and hyperthyroidism can cause diffuse hair shedding including eyebrow thinning. Thyroid hormones regulate cell growth and metabolism across the body, and skin appendages — including hair follicles — are particularly sensitive to hormonal imbalance 2Ref 2Hussein RS, Atia T, Bin Dayel S (2023).Impact of Thyroid Dysfunction on Hair Disorders.Thyroid hormones regulate cell growth and metabolism; both hypothyroidism and hyperthyroidism can cause diffuse hair shedding including eyebrow thinning. Hypothyroidism is especially associated with the outer-third eyebrow pattern.

Because thyroid dysfunction is common and straightforwardly treated once diagnosed, it is usually among the first tests ordered when a clinician evaluates unexplained eyebrow or scalp hair loss. American Thyroid Association guidelines support TSH measurement as the primary screening test 3Ref 3Aboalola D, Aouabdi S, Ramadan M, et al. (2023).An Update on Alopecia and its Association With Thyroid Autoimmune Diseases.Alopecia is correlated with thyroid autoimmune diseases including Hashimoto thyroiditis and Graves disease. If you also experience fatigue, unexplained weight changes, cold intolerance, dry skin, or constipation alongside your eyebrow changes, mention all of these together — they form a coherent clinical picture that makes thyroid evaluation a priority.

Could this be alopecia areata?

Alopecia areata (AA) is an autoimmune condition in which the immune system targets hair follicles. It classically causes patchy scalp hair loss but frequently involves the eyebrows and eyelashes as well — in one large cohort, eyebrow involvement was documented in 19–63% of patients with AA, with rates varying by population studied 4Ref 4Nguyen B, Hu JK, Tosti A (2022).Eyebrow and Eyelash Alopecia: A Clinical Review.Alopecia areata presents as bilateral patchy eyebrow loss; eyebrow involvement documented in 19–63% of AA patients across cohorts; trichoscopy shows cadaverized hairs and yellow dots. Eyebrow involvement in alopecia areata typically presents as bilateral, patchy loss rather than the gradual uniform thinning seen with hormonal or nutritional causes 4Ref 4Nguyen B, Hu JK, Tosti A (2022).Eyebrow and Eyelash Alopecia: A Clinical Review.Alopecia areata presents as bilateral patchy eyebrow loss; eyebrow involvement documented in 19–63% of AA patients across cohorts; trichoscopy shows cadaverized hairs and yellow dots.

When AA affects the entire scalp it is called alopecia totalis; when it involves the full body it is alopecia universalis. A personal or family history of autoimmune conditions — including thyroid disease, vitiligo, or rheumatoid arthritis — raises the likelihood of an immune-driven mechanism. Alopecia areata is managed by dermatologists, and newer JAK-inhibitor therapies have substantially changed the treatment landscape in recent years 5Ref 5Dainichi T, Iwata M, Kaku Y (2024).Alopecia areata: What's new in the diagnosis and treatment with JAK inhibitors?.JAK inhibitor therapies have substantially changed the treatment landscape for alopecia areata.

What is frontal fibrosing alopecia, and why does it affect eyebrows?

Frontal fibrosing alopecia (FFA) is a scarring (cicatricial) alopecia that causes progressive recession of the hairline alongside eyebrow loss. It has been increasingly recognized over the past two decades and primarily affects postmenopausal women, though it also occurs in premenopausal women and men 6Ref 6Multiple authors (2022).Frontal fibrosing alopecia: A review of disease pathogenesis.FFA primarily affects postmenopausal women; incidence has increased worldwide; frontotemporal hairline regression and eyebrow loss are hallmark features. The eyebrows are involved in 63–83% of FFA cases, and in roughly one-third of patients, eyebrow loss appears *before* the hairline begins to recede — meaning it can be the earliest visible sign of the disease 7Ref 7Verma S, Marak A, Paul D (2025).Frontal Fibrosing Alopecia: A Comprehensive Review with Recent Updates.Eyebrow involvement occurs in 63–83% of FFA cases; can appear before hairline recession in ~33% of patients; patients with darker skin tones may present differently8Ref 8Imhof RL, Villalpando B, Proffer S, Cantwell H, Tolkachjov S, Torgerson R (2022).Eyebrow hair loss as a prognostic factor for frontal fibrosing alopecia.Eyebrow hair loss (madarosis) as a prognostic indicator in frontal fibrosing alopecia.

Dermoscopic (trichoscopic) examination of affected eyebrows shows characteristic findings — yellow dots, dystrophic hairs, and altered regrowth direction — that help distinguish FFA from other causes and can support early diagnosis 9Ref 9Anzai A, Pirmez R, Vincenzi C, Fabbrocini G, Romiti R, Tosti A (2021).Trichoscopy findings of frontal fibrosing alopecia on the eyebrows: A study of 151 cases.Dermoscopic examination of FFA-affected eyebrows shows yellow dots, dystrophic hairs, and altered regrowth direction; supports early diagnosis and distinction from other causes. FFA is a scarring condition, which means delay in diagnosis risks permanent follicle loss; early referral to a dermatologist is important if FFA is suspected.

Patients with darker skin tones may have less visually obvious inflammation at the hairline, making explicit mention of eyebrow changes to a clinician especially important 7Ref 7Verma S, Marak A, Paul D (2025).Frontal Fibrosing Alopecia: A Comprehensive Review with Recent Updates.Eyebrow involvement occurs in 63–83% of FFA cases; can appear before hairline recession in ~33% of patients; patients with darker skin tones may present differently.

What skin conditions can thin the brows?

Seborrheic dermatitis — a common inflammatory condition related to dandruff — consistently involves the eyebrow area alongside the scalp and nasolabial folds. In affected patients, eyebrow scaling, itching, and redness are typical, and chronic inflammation can contribute to temporary thinning 10Ref 10Polaskey MT, Chang CH, Daftary K, Fakhraie S, Miller CH, Chovatiya R (2024).The Global Prevalence of Seborrheic Dermatitis: A Systematic Review and Meta-Analysis.Seborrheic dermatitis affects approximately 1–5% of adults; eyebrow area is a characteristic site of involvement due to sebum-rich location. Seborrheic dermatitis affects approximately 1–5% of adults and is more common in males 10Ref 10Polaskey MT, Chang CH, Daftary K, Fakhraie S, Miller CH, Chovatiya R (2024).The Global Prevalence of Seborrheic Dermatitis: A Systematic Review and Meta-Analysis.Seborrheic dermatitis affects approximately 1–5% of adults; eyebrow area is a characteristic site of involvement due to sebum-rich location.

Atopic dermatitis (eczema), psoriasis, and contact dermatitis from skincare products, cosmetics, or brow treatments can also cause local inflammation that disrupts the follicle environment. These conditions are generally identifiable by visible skin changes — redness, flaking, or irritation — rather than isolated hair loss on otherwise normal-looking skin.

Do nutritional deficiencies cause eyebrow thinning?

Iron deficiency is the best-studied nutritional contributor to hair loss. A systematic review and meta-analysis of 36 studies found that women with nonscarring alopecia had significantly lower serum ferritin levels than controls 11Ref 11Treister-Goltzman Y, Yarza S, Peleg R (2021).Iron Deficiency and Nonscarring Alopecia in Women: Systematic Review and Meta-Analysis.Women with nonscarring alopecia had significantly lower serum ferritin values than controls across 36 studies (10,029 participants). Iron deficiency can cause diffuse shedding that involves both scalp and eyebrow hair; testing serum ferritin alongside a complete blood count is a standard part of the workup 12Ref 12Zhang D, LaSenna C, Shields BE (2023).Serum Ferritin Levels: A Clinical Guide in Patients With Hair Loss.Low serum ferritin is a sensitive and specific marker for iron deficiency in hair loss workup; testing serum ferritin alongside CBC is standard practice.

Vitamin D and zinc deficiencies have also been associated with hair loss, and prolonged caloric restriction or elimination diets can deprive follicles of the building blocks they need. Hormonal shifts — including menopause, polycystic ovary syndrome (PCOS), and the postpartum period — affect eyebrows as well as scalp hair through overlapping mechanisms.

Can over-plucking permanently damage eyebrows?

Over-plucking is a common history in people with thin brows. In most cases, the thinning is reversible once the habit stops. However, years of repetitive, aggressive plucking can cause cumulative follicle trauma that leads to permanent thinning or patchy regrowth in some individuals. The mechanism resembles traction-type injury — repeated mechanical disruption of the follicle eventually impairs its regenerative capacity 13Ref 13Billero V, Miteva M (2018).Traction alopecia: the root of the problem.Repetitive mechanical trauma to follicles can cause cumulative damage leading to permanent thinning — the mechanism underlying over-plucking injury. If a long plucking history is the primary explanation, there will typically be no systemic symptoms and no involvement of other body sites.

What will a clinician likely assess or test?

A clinician evaluating eyebrow thinning will typically begin with a targeted history — timing, pattern (inner vs. outer vs. uniform), whether it is unilateral or bilateral, associated symptoms, medications, and personal or family autoimmune history. Examination of the brow skin itself (for redness, scaling, a pale band at the hairline margin) and of the hairline, scalp, and eyelashes can significantly narrow the differential.

Common laboratory tests include: - TSH and free T4 — to rule out thyroid dysfunction, one of the most common and correctable causes - CBC and serum ferritin — to assess for iron deficiency or anemia - Vitamin D and zinc levels — when nutritional deficiency is clinically suspected - ANA panel — if lupus, Sjogren's syndrome, or another autoimmune condition is in the differential

A dermatologist may use dermoscopy of the brow skin to evaluate follicle patterns and distinguish scarring from non-scarring causes — an important distinction because scarring alopecias like FFA require prompt management to limit permanent loss. A small skin biopsy is occasionally needed for a definitive diagnosis 9Ref 9Anzai A, Pirmez R, Vincenzi C, Fabbrocini G, Romiti R, Tosti A (2021).Trichoscopy findings of frontal fibrosing alopecia on the eyebrows: A study of 151 cases.Dermoscopic examination of FFA-affected eyebrows shows yellow dots, dystrophic hairs, and altered regrowth direction; supports early diagnosis and distinction from other causes.