What should you know about hypothyroidism and brittle hair?

Thyroid hormone affects the activity of many tissues, and an underactive thyroid may be accompanied by dry skin, reduced energy, feeling cold, constipation, or hair that becomes coarse, dry, or fragile. Hair brittleness can also follow heat styling, chemical treatments, tight hairstyles, scalp conditions, nutritional problems, or other illness. A clinician uses the wider pattern and thyroid blood tests to work out what is happening. Learn about [Hypothyroidism](/conditions/hypothyroidism/).

Hair usually changes gradually, and improvement may take time after the underlying problem is treated because existing hair has already formed. Breaking hair is different from shedding from the root, so describe both clearly during an appointment.

Use gentle washing, conditioner, and a wide-toothed comb; reduce high heat, bleaching, relaxing, and tight pulling. Avoid taking thyroid hormone or high-dose hair supplements without advice. Record when the change began, whether hair is breaking or shedding, and any recent illness, diet change, pregnancy, medicine, or styling treatment. Ask for thyroid testing if symptoms fit.

Arrange a review for persistent brittleness, noticeable thinning, scalp pain, scaling, sores, or patchy hair loss. Seek faster assessment for sudden extensive shedding, swelling of the face or neck, severe weakness, confusion, or breathing difficulty. These features may need attention beyond routine hair care.

Ask whether your hair pattern suggests breakage or root shedding, whether thyroid tests are appropriate, and whether another cause should be checked. Ask which products or supplements are safe with your medicines and what improvement to expect after treatment.