The thyroid gland controls your metabolism, and both an underactive and an overactive thyroid can affect hair. Thyroid-related hair loss is common, and it often improves when the thyroid condition is treated. This guide explains the connection, the signs, and why the thyroid itself needs a physician's care.
How the thyroid affects hair
Thyroid hormones help regulate how cells grow and renew, including hair follicle cells. When levels are too low (hypothyroidism) or too high (hyperthyroidism), more hairs can enter the resting phase and shed, causing diffuse thinning across the scalp rather than a specific pattern.
Signs of hypothyroidism
- Diffuse hair thinning, dry or coarse hair, and sometimes thinning of the outer eyebrows
- Fatigue and feeling cold
- Weight gain and constipation
- Dry skin
- Heavier or irregular periods
Signs of hyperthyroidism
- Diffuse hair thinning and fine, soft hair
- Racing or irregular heartbeat
- Weight loss despite normal eating
- Heat intolerance and sweating
- Anxiety, tremor and trouble sleeping
How it is diagnosed
A doctor diagnoses thyroid conditions with blood tests, usually starting with TSH and often free T4. Autoimmune thyroid conditions, such as Hashimoto's thyroiditis and Graves' disease, are common causes and are also associated with alopecia areata, a separate cause of patchy hair loss.
Treatment
The main treatment for thyroid-related hair loss is treating the thyroid condition itself, managed by a primary care doctor or endocrinologist. Once hormone levels are back in range, shedding often settles, but hair regrows slowly, so improvement takes time. Some thyroid medications can themselves cause temporary shedding when started or adjusted. Do not change thyroid medication on your own.
Thyroid conditions can coexist with other causes, such as low iron or pattern hair loss. If thinning continues after the thyroid is well controlled, other causes should be considered. See ferritin and hair loss and hormonal hair loss in women.
When to see a doctor
See a doctor if you have hair loss along with symptoms like those above. Seek prompt care for a racing heartbeat, chest pain, severe fatigue or confusion.
Next step
A thyroid condition needs your own doctor's care. If your thyroid is being managed and you want a licensed provider to review ongoing thinning, start your online consultation.
Prescription required for prescription treatment. A licensed provider decides whether treatment is appropriate. Individual results vary. Prescribed Essence currently serves patients in California, Colorado, Florida and New York.
