In short: yes, usually. Both an underactive thyroid (hypothyroidism) and an overactive one (hyperthyroidism) can cause all-over hair shedding. Once thyroid levels are brought back to normal with treatment, hair usually recovers over several months. If it doesn't, there may be a second cause, such as low iron, female pattern hair loss or alopecia areata.
This page applies to men and women. Thyroid problems are much more common in women.
How the thyroid affects hair
Thyroid hormones help control the hair growth cycle. When levels are too low or too high, more hairs move into the resting (shedding) phase at the same time. The result is diffuse shedding, similar to telogen effluvium.
Signs it might be your thyroid
| Underactive (hypothyroid) | Overactive (hyperthyroid) |
|---|---|
| Tiredness, feeling cold | Feeling hot, sweating |
| Weight gain, constipation | Weight loss, loose stools |
| Dry skin, coarse, dry hair | Fine, thin hair |
| Thinning of the outer third of the eyebrows | Fast heartbeat, tremor, anxiety |
| Heavy or irregular periods | Lighter or irregular periods |
Thyroid conditions are often autoimmune (Hashimoto's, Graves'), and people with them have a higher chance of alopecia areata too.
Tests to ask for
- TSH: the main screening test
- Free T4 (± free T3), if TSH is abnormal
- Anti-TPO antibodies: autoimmune thyroid disease
- Ferritin and CBC: low iron often coexists and slows hair recovery
Stop biotin supplements a few days before thyroid tests (ask your doctor). High-dose biotin can make results look falsely abnormal.
Treatment and regrowth
- Treat the thyroid first. Levothyroxine for an underactive thyroid; for an overactive thyroid, medicines such as carbimazole or other treatment from an endocrinologist.
- Regrowth timeline: shedding usually slows within 2–3 months of stable normal levels, with visible regrowth over 6–12 months.
- Shedding when starting treatment: some people notice extra shedding in the first weeks or months of thyroid treatment. This is usually temporary, but keep your doctor informed.
- Still thinning after 6–12 months of normal levels? Ask about low iron, vitamin D, female or male pattern hair loss, or alopecia areata. Minoxidil may help if pattern loss is also present. → Minoxidil
What you can do meanwhile
- Take your thyroid medicine consistently, as directed (usually on an empty stomach, apart from calcium or iron supplements).
- Get ferritin checked and treated if low.
- Be gentle with hair: avoid tight styles, harsh chemical treatments and excessive heat while it recovers.
- Oils and hair masks can make hair feel better, but they won't fix the thyroid cause.
FAQs
Will thyroid hair loss grow back? In most people, yes, once levels are controlled. It takes months, not weeks.
Does levothyroxine cause hair loss? Some people notice shedding when starting or changing the dose, usually temporary. Don't stop your medicine without talking to your doctor.
I have thyroid disease and my parting is widening. Is that the thyroid? Possibly both. Thyroid shedding is usually all over. A widening parting suggests female pattern hair loss as well. → Female pattern hair loss
See a doctor soon if you have: round bald patches that appear suddenly · hair coming out in clumps · redness, pain, pus, scaling or scarring on the scalp · hair loss with fever, weight loss, irregular periods, acne or new facial hair · eyebrow or eyelash loss · hair loss in a child.
Medical review pending: not yet reviewed by a dermatologist. Medical disclaimer
Discussion
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