The short explanation
Thinning of the outer part of the eyebrows, along with dry, coarse hair, is a change sometimes seen with an underactive thyroid. It is not specific, though; eyebrows also thin with age, after repeated threading, with eczema or with iron deficiency. A thyroid blood test is a reasonable way to check, especially if you have other symptoms. If the thyroid is underactive and is treated, hair often improves gradually over months, because hair grows slowly.
What depends on your situation
The parts of this that change from woman to woman. Uncertainty is stated, not hidden.
- Other signs that support a thyroid cause include tiredness, feeling cold, constipation, dry skin, weight gain and heavier periods. In your forties, perimenopause can also change hair and skin, and low iron from heavy periods is common.
- Your doctor may check TSH, a blood count and ferritin together, because these causes often overlap.
- Avoid applying unknown oils or creams to the eyebrows in the hope of regrowth; check the cause first.
What this answer cannot determine
The boundary of online education. These need a clinician who can see you.
- This answer cannot tell you why your eyebrows are thinning. A doctor's examination and blood tests are needed.
Questions for your clinician
Take these with you. You can add any of them to an appointment card.
- Could my thyroid be causing this, and which tests should I have?
- Should my iron and ferritin be checked as well?
- Could perimenopause be part of this?
- How long would hair take to improve if the thyroid is treated?
When to seek help
Clinician-approved guidance for this topic. When in doubt, being seen is never the wrong choice.
Book an appointment soon
- See a doctor within a few days if you also have marked tiredness, swelling in your neck or very heavy periods.
Raise it at a routine appointment
- Book a routine visit for thyroid and blood tests if the hair changes have built up over months.
Sources
The evidence this explanation is built on.
- Hypothyroidism MedlinePlus (NIH)
- Underactive thyroid (hypothyroidism) NHS
- Thyroid tests MedlinePlus (NIH)
Who wrote and reviewed this
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- Author
- AskHer Editorial (AI-assisted draft) AskHer's editorial team — not an individual clinician Works in English, தமிழ், हिन्दी
- Clinical reviewer
- Nobody yet No clinician has signed this answer off, and no person on the editorial team has read it yet. That is what the “Written with AI assistance” label means. It is queued for an editor to read, and then for a clinician who works in this area. The sources it was drafted against are listed above.
- Review status
- Written with AI assistance — not yet reviewed by a person
- Last reviewed
- Not yet reviewed by a person
- Version
- 1
Correction history
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No corrections have been made since this answer was first published.
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