There are a few different causes of hyperthyroidism: • Graves’ disease Graves’ disease is one of the more common causes of hyperthyroidism, this condition is an autoimmune disorder which is when the immune system begins to attack the thyroid and causes it to increase its production of the thyroid hormone. • Overactive thyroid nodules Overactive thyroid nodules are when there are lumps within the thyroid, this is also quite common, and normally not cancerous. If one or more nodules become overactive, this is when it can begin to overproduce the thyroid hormone. • Thyroiditis is when the thyroid gland is inflamed This inflammation of the thyroid gland can cause some types to leak out into the thyroid gland and straight into the bloodstream. Due to this, you may begin to develop signs and symptoms of hyperthyroidism. These types of thyroiditis can cause hyperthyroidism, which may include: • Subacute thyroiditis causes painfully inflamed and enlarged thyroid • Postpartum thyroiditis, which usually develops after a woman gives birth • Painless thyroiditis is similar to postpartum thyroiditis; however, it occurs without pregnancy and enlarges the thyroid painlessly. Thyroiditis can also cause symptoms of hypothyroidism, which is an underactive thyroid. • Overproduction of iodine The thyroid uses iodine to create the thyroid hormone. Depending on how much iodine the body consumes can affect how much of the hormone the thyroid keeps creating. Large consumption amounts of iodine can cause the thyroid to end up overproducing thyroid hormones. • Too much thyroid hormone medicine If you have been diagnosed with hypothyroidism, and you over-consume the allotted amount for your condition, you may take too much, which can cause hyperthyroidism to occur.     • Noncancerous tumor in the pituitary gland      While this is quite rare, noncancerous tumors of the pituitary gland, which are located at the base of the brain, can end up causing hyperthyroidism.