- Heart complications include abnormal heart rhythm (as in atrial fibrillation, premature ventricular contractions) which may result in heart failure.
- Hypokalemic (an abnormally low concentration of potassium ions in blood) periodic paralysis occurs in about 15% of Asian or Native American men. The condition presents with sudden paralysis and a few hyperthyroidism symptoms. It is usually precipitated by intravenous dextrose, oral carbohydrate or vigorous exercise. Attack usually lasts for 7-72 hours.
- Decreased sexual desire, low sperm count, impotency or gynecomastia (abnormal enlargement of breasts in males) in males.
- Thyroid storm