What are the causes of hyperthyroidism?

Stephanie Smooke-Praw, MD
Endocrinology Diabetes & Metabolism
The main causes ofhyperthyroidism, or overactive thyroid, are an autoimmune condition called Graves’ disease, toxic single nodule or multiple toxic nodules, or a transient inflammation of the thyroid gland called thyroiditis. Identifying the underlying cause of hyperthyroidism is very important as each condition is managed differently. Management may include anti-thyroid medication, radioactive iodine, surgery or monitoring.
The most common cause of hyperthyroidism is an autoimmune condition called Graves' disease, which causes your thyroid to produce too much thyroid hormone. Certain viral illnesses or thyroid cancers can also cause hyperthyroidism. 
Hyperthyroidism, or overactive thyroid, can be caused by a number of conditions affecting the thyroid. Common causes of hyperthyroidism include Graves disease, toxic nodule, toxic multinodular goiter, thyroiditis, excess TSH secretion, taking excess thyroid hormone, or excess iodine intake.
Graves disease is an autoimmune disorder characterized by generalized overactivity of the thyroid gland. It is more common in women and may be hereditary. Alternatively, the overactivity may be centered in areas of overgrowth, called nodules. When there is one or more overfunctioning nodules, this is called a toxic nodule or toxic multinodular goiter. Thyroiditis, or inflammation of the thyroid, may be associated with both hyper and hypothyroidism. Thyroiditis may occur following a viral infection or after pregnancy. Rarely, excess TSH secretion from the pituitary gland in the brain may cause hyperthyroidism. Excess iodine intake is also rare, and may be due to specific drugs, such as amiodarone.
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Diseases of thyroid function: Hyperthyroidism

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