Can Thyroid Problems Cause Hair Loss?

Yes, thyroid problems can cause significant hair loss in both men and women. Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) disrupt the normal hair growth cycle. The thyroid hormones T3 and T4 directly regulate hair follicle function, and imbalances can cause hair to become thin, brittle, and fall out more rapidly than normal. Hair thinning can occur with thyroid disorders, but estimates vary depending on the specific condition and population studied. The hair loss typically affects the entire scalp rather than creating patchy bald spots, and eyebrow thinning is also common. Treating the thyroid condition may allow hair growth to recover, but improvement often takes several months and varies from person to person. Persistent hair loss may have another or an additional cause and should be evaluated by a clinician.