Medical conditions and situations that can cause hyperthyroidism include: Graves’ disease: In this disorder, your immune system attacks your thyroid. This makes your thyroid create too much thyroid hormone. Graves’ disease is a hereditary condition (passed down through a family). If a member of your family has Graves’ disease, there’s a chance others in the family could have it, too. It’s more common in people assigned female at birth than people assigned male at birth. Graves’ disease is the most common cause of hyperthyroidism, making up about 85% of cases. Thyroid nodules: A thyroid nodule is a lump or growth of cells in your thyroid gland. They can produce more hormones than your body needs. Thyroid nodules are rarely cancerous. Thyroiditis: Thyroiditis is inflammation of your thyroid gland, which may be painful or painless (silent). It may happen within a year of delivering a baby (postpartum thyroiditis). After you experience thyroiditis, your thyroid may be unable to recover, which would lead to hypothyroidism. Consuming excess iodine: If you’re at risk for hyperthyroidism and consume too much iodine (through your diet or medications), it can cause your thyroid to produce more thyroid hormone. Iodine is a mineral that your thyroid uses to create thyroid hormone. Receiving intravenous iodinated contrast (iodine “dye”) may also cause hyperthyroidism. Amiodarone, a medication that contains a high amount of iodine, may also cause hyperthyroidism.