Thyroid Disease and Eyelash Loss: Can an Underactive Thyroid Make Lashes Fall Out?

You notice a gap along the lash line, then another. Your brows look thinner at the outer edges, your skin feels drier than usual, and you are more tired than a normal week explains. It is natural to wonder whether the pieces are connected. Sometimes they are, and the thyroid is one of the first places doctors look.

The thyroid is a small gland at the base of the neck that releases hormones the body uses to regulate energy and growth, including the growth of hair. When hormone levels drift too low or too high, hair can become dry, fine, or sparse. Lashes and brows are hair too, so they can be caught up in the same change.

That said, lash thinning has many possible causes, and a thyroid problem is only one of them. This guide explains what the medical literature says about the connection, what thyroid-related lash loss tends to look like, how doctors confirm or rule it out, and what you can realistically expect after treatment.

Medical sources describe dry, thinning hair as one of the many underactive thyroid symptoms and causes, but they also stress that symptoms alone cannot confirm a diagnosis. Blood tests are what settle the question, so the goal of this article is to help you ask better questions, not to diagnose yourself.

Key Takeaways

• Thyroid problems can disrupt the hair growth cycle, and eyelash and eyebrow loss has been reported in people with both underactive and overactive thyroid conditions.
• Thinning at the outer third of the eyebrows is a classic clue, but it does not prove a thyroid disorder.
• Many other conditions cause similar lash loss, including alopecia areata, eyelid inflammation, hair pulling, and medicines.
• A simple blood test, usually starting with TSH, is how doctors check thyroid function.
• High-dose biotin supplements can interfere with some thyroid lab results, so tell your clinician what you take.
• When thyroid disease is the cause, lashes may regrow over months once hormone levels are managed, but regrowth varies and is not guaranteed.
• No lash serum treats a thyroid condition. Persistent lash loss deserves a medical visit.

How can the thyroid affect eyelashes?

Every hair follicle cycles through growth, transition, and rest phases. The lash version of that cycle is short compared with scalp hair, which is one reason lashes stay at a modest length. You can read the stages in our guide to the eyelash growth cycle.

A medical review of lash and brow loss (madarosis) notes that thyroid hormone receptors have been found in hair follicles, which helps explain why hormone imbalance can matter. According to that review, thyroid-related hair loss has been linked to the growth phase ending early and to follicles failing to restart growth on time.

In practical terms, a follicle that stays in the resting phase longer, or restarts late, produces fewer and finer hairs. On the lash line that can look like a gradual loss of density rather than a sudden bald patch.

Which thyroid conditions are involved?

Two broad groups come up in the literature:

• Hypothyroidism (underactive thyroid): hormone levels are too low. The NIDDK lists dry, thinning hair among its possible symptoms, along with fatigue, cold intolerance, and dry skin. One academic health system reports that about half of people with hypothyroidism notice some hair loss, ranging from mild to widespread.
• Hyperthyroidism (overactive thyroid): hormone levels are too high. Clinical overviews describe hair that becomes fine and brittle and may shed more.

Autoimmune thyroid disease, such as Hashimoto’s thyroiditis or Graves’ disease, can also sit alongside other autoimmune conditions that affect hair. That overlap is part of why a doctor may look at the whole picture instead of the lashes alone.

What does thyroid-related lash loss look like?

There is no single pattern, but clinicians describe a few features that raise suspicion.

Signs on the face

• Gradual thinning across the lash line instead of one sharp, isolated bald spot.
• Loss of the outer third of the eyebrows, sometimes called the Hertoghe sign.
• Puffiness around the eyes. A published case report of severe, uncontrolled hypothyroidism described swelling around the eyes together with extensive loss of upper lashes.

Signs elsewhere in the body

• Persistent tiredness, sensitivity to cold, constipation, or unexplained weight change.
• Dry, coarse skin and brittle nails.
• Heavier or irregular periods.
• For an overactive thyroid: a racing heartbeat, heat intolerance, tremor, or unplanned weight loss.

None of these is specific. Fatigue and dry skin are common and often have unrelated causes, which is exactly why testing matters.

What else can look like thyroid lash loss?

Before assuming the thyroid is responsible, it helps to know how crowded this field is. A review of madarosis groups causes into categories including skin disorders, infection, medicines, nutritional problems, trauma, and systemic illness. Common look-alikes include:

• Autoimmune hair loss. Alopecia areata can remove lashes and brows, often in patches.
• Eyelid inflammation. Crusty, itchy lids and blepharitis can damage lashes through irritation and rubbing.
• Hair pulling. An urge to pull lashes, known as trichotillomania, can look like true loss. In one published case, a clinician first suspected pulling, then found a thyroid problem, and lashes returned with treatment.
• Medical treatment. Some therapies cause temporary lash shedding, as covered in our post on chemotherapy eyelash loss.
• Sparse lashes from birth or long-standing thinness. Our explainer on eyelash hypotrichosis covers how that differs from active shedding.
• Cosmetic habits. Harsh removal, heavy extensions, and aggressive curling can break or pull lashes.

Several causes can overlap in the same person, which is another reason to get a proper assessment instead of guessing.

How do doctors check for a thyroid cause?

An appointment about lash loss usually starts with questions. Expect your clinician to ask when the loss began, whether it affects brows or scalp hair, what medicines and supplements you take, and whether anyone in your family has thyroid disease. In the published cases mentioned above, a family history of thyroid problems and mild heat intolerance were important clues.

The blood tests

The NIDDK explains that a hypothyroidism diagnosis cannot rest on symptoms alone and that doctors typically use thyroid blood tests, sometimes with imaging. The usual first step is a TSH (thyroid-stimulating hormone) test, often followed by thyroxine (T4) levels or thyroid antibody tests if the first result is abnormal. Your clinician decides which tests fit your situation.

Why biotin matters before testing

Many hair, skin, and nail supplements contain biotin, also called vitamin B7. The FDA has warned that biotin can interfere with certain lab tests and produce incorrect results. Some of the tests involved measure thyroid hormones and thyroid-related antibodies. The agency noted that some supplements contain far more biotin than the recommended daily value, and that very high intake is the main concern, not standard multivitamin amounts.

If you take a biotin product, tell the clinician ordering your tests and the lab. They may suggest pausing it for a few days beforehand. Do not stop prescribed medicines without medical advice, and keep in mind that this decision belongs to your clinician. If you are curious what nutrients do and do not do for lashes, see our overview of vitamins for lashes.

Will lashes grow back after thyroid treatment?

Often, but not always, and rarely quickly. Thyroid conditions are usually treated by correcting hormone levels, for example with replacement hormone for an underactive thyroid. Clinical overviews describe hair loss related to thyroid problems as often improving after the underlying condition is treated, though regrowth takes months and may be incomplete.

Published cases show the range. In one, lashes began to return roughly twelve weeks after treatment started. In another, lashes had not regrown at the time of reporting despite treatment. A single case is not a prediction for you, but it illustrates why patience and follow-up are part of the plan.

Because lashes grow slowly, the visible result lags behind the blood work. If your thyroid numbers improve but your lashes do not, ask whether another cause, such as alopecia areata or eyelid disease, could be contributing.

What can you do while you wait?

Whatever the cause, protecting the lashes you have is sensible. Gentle habits will not fix a thyroid problem, but they stop you from adding damage on top of it.

• Remove eye makeup with a soft pad and a gentle remover, without tugging.
• Take a break from lash extensions, glue, and heated curlers while lashes are fragile.
• Avoid rubbing your eyes and lids.
• Keep your thyroid medicine and follow-up appointments on schedule if you have been prescribed treatment.
• Ask your clinician about nutrition only when a deficiency has been found. Extra supplements are not automatically helpful.

For a broader look at care and expectations, our guide on how to regrow lost eyelashes covers the general picture, and our overview of eyelash loss lists more everyday causes.

Where do lash serums fit in?

It is worth being clear here. A lash serum, whether cosmetic or prescription, does not treat thyroid disease, and it is not a substitute for finding out why lashes are falling out. Bimatoprost is a prescription drug in the US, and its effect on lashes was studied in people with sparse lashes in general, not as a therapy for thyroid-related loss. Our article on bimatoprost for eyelashes explains what the evidence does and does not show.

If you are considering any lash product while a medical cause is still being sorted out, talk to your clinician first. Treat any manufacturer claim about results as a claim, not a guarantee, and read the label for active ingredients before you apply anything near your eyes.

When should you see a doctor?

Book an appointment sooner rather than later if you notice any of the following:

• Lash or eyebrow loss that lasts more than a few weeks or keeps spreading.
• Loss together with fatigue, weight change, temperature sensitivity, or heart palpitations.
• Red, swollen, painful, or crusted eyelids, or changes in vision.
• Bald patches on the scalp or elsewhere on the body.
• Lashes growing inward or irritating the eye surface.

A primary care clinician can order thyroid tests, and an eye doctor or dermatologist can examine the lids and follicles. This article is general information, not medical advice. Please talk to a licensed clinician about any eye or eyelid concern.

Frequently Asked Questions

Can an underactive thyroid cause eyelash loss?

Yes, it has been reported. Medical literature on madarosis lists thyroid disease among the possible causes, and case reports describe lash loss in people with uncontrolled hypothyroidism. It is only one of many causes, so testing is needed before drawing a conclusion.

Can an overactive thyroid cause lash thinning too?

Clinical overviews link both underactive and overactive thyroid conditions with hair thinning or shedding. The pattern and the associated symptoms differ, which is why your doctor will look at the full picture and blood results.

Which blood test checks the thyroid?

TSH is usually the first test. Depending on the result, your clinician may add T4, T3, or thyroid antibody tests. Tell them about any biotin supplements beforehand, since biotin can affect some lab results.

How long do lashes take to regrow after treatment?

There is no fixed timeline. Reports describe regrowth over months, and in some cases it is partial or slow. Lashes cycle slowly, so improvement often shows well after hormone levels are corrected.

Is eyebrow thinning a sign of thyroid disease?

Thinning of the outer third of the brows is a recognized clue, but it is not proof. Aging, over-plucking, alopecia areata, and skin conditions can cause the same look. Only testing can say whether the thyroid is involved.

Should I take biotin for thyroid-related lash loss?

Do not start high-dose biotin without speaking to a clinician. It has not been shown to fix thyroid-related lash loss, and it can interfere with the very tests used to check your thyroid.

Sources

• National Institute of Diabetes and Digestive and Kidney Diseases (NIH), “Hypothyroidism (Underactive Thyroid),” niddk.nih.gov.
• Jordan DR, “Eyelash Loss,” Seminars in Plastic Surgery, 2007, via PubMed Central (pmc.ncbi.nlm.nih.gov, PMC2884829).
• “Eyelash Loss: An Unusual Manifestation of Uncontrolled Hypothyroidism,” case report, Cureus (cureus.com).
• Review article on madarosis (eyelash and eyebrow loss) classifying causes, including thyroid disease (published PDF review, dr-jetskeultee.nl).
• FDA safety communications on biotin interference with laboratory tests (2017 and 2019 updates), as reported by Healio and Lab Tests Online (healio.com, labtestsonline.org).
• UC Health, “Hypothyroidism,” patient information on hair loss in hypothyroidism (uchealth.org).