Hashimoto’s thyroiditis is an autoimmune disease in which T-cells and antibodies attack thyroid tissue, causing progressive inflammation and fibrosis. Over time, the gland’s ability to produce T3 and T4 declines, resulting in hypothyroidism. It is the most common thyroid condition in iodine-sufficient regions and affects women around 7–10 times more often than men.
Diagnosis combines TSH (elevated as the pituitary tries to stimulate the failing gland), free T4 (low or low-normal), and antibody tests — anti-TPO (thyroid peroxidase) and anti-TG (thyroglobulin) antibodies. Antibodies can be elevated for years before the TSH shifts.
The nutrition role in Hashimoto’s is limited but not zero. Selenium (from Brazil nuts in moderation — two to three nuts/day — seafood, and meat) supports the conversion of T4 to active T3 and has modest evidence for reducing TPO antibody levels in selenium-deficient populations. Iodine adequacy is important — severe deficiency worsens autoimmune thyroid conditions — but high-dose iodine supplements can trigger or worsen flares. Supplementation without testing is not recommended.
Gluten-free diets are widely promoted for Hashimoto’s. The evidence is limited to people with confirmed coeliac disease or dermatitis herpetiformis — both of which are autoimmune conditions with documented thyroid disease overlap. Routine gluten elimination for Hashimoto’s without coeliac diagnosis is not supported by robust evidence.
Treatment is levothyroxine replacement when TSH indicates clinical hypothyroidism. Work with your endocrinologist and a registered dietitian.