The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hyperthyroidism occurs when the thyroid gland becomes overactive and produces too much thyroid hormone.

The Thyroid Gland
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Hyperthyroidism may be caused by:

  • Graves' disease —an autoimmune disorder that occurs when the immune system produces antibodies that attack cells of the thyroid gland
  • Thyroid nodules:
    • Toxic uninodular goiter—a single area/nodule in the thyroid gland is overactive
    • Toxic multinodular goiter—multiple nodules in the thyroid gland which overproduce thyroid hormone
  • Thyroiditis—inflammation of the thyroid that may later lead to hypothyroidism
  • Taking too much thyroid hormone—very rarely from meat sources contaminated by animal thyroid glands