How does Hashimoto's autoimmune disease affect the thyroid?
Hashimoto's is the autoimmune cause of most hypothyroidism. Diagnosis combines elevated TSH, low Free T4, and positive TPO or thyroglobulin antibodies. Treatment is thyroid hormone replacement.
Full answer
Hashimoto's thyroiditis is an autoimmune disease in which the immune system progressively destroys thyroid tissue. It is the most common cause of hypothyroidism in iodine-sufficient regions. Diagnosis combines elevated TSH, low or low-normal Free T4, and positive TPO antibodies (90%+ of cases) or thyroglobulin antibodies. Symptoms — fatigue, weight gain, cold intolerance, brain fog, hair thinning, depression — develop slowly as thyroid output declines. Treatment is levothyroxine titrated to TSH and symptom response. oMeds provider review individualizes dosing using TSH, Free T4, Free T3, and (when conversion problems are suspected) Reverse T3.
Educational. Not a substitute for individualized provider review.
- TPO Antibodies — Primary source · oMeds
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29