Health Conditions

What causes it?

Numerous factors have been identified for causing hyperthyroidism.

1. Graves' Disease
   
   Graves' disease occurs when the immune or protective mechanisms of the body mistakenly activate the thyroid gland to release thyroid hormone. This is the primary cause of hyperthyroidism and usually causes protrusion of the eyes, redness on the front of the legs, and other signs and symptoms associated with hyperthyroidism as listed below.
   
   
2. Pituitary adenoma
   
   A pituitary adenoma is a tumor that secretes a hormone that activates the thyroid gland above and beyond normal stimulation. This causes the release of thyroid hormone in excess and the signs and symptoms of hyperthyroidism.
   
   
3. Pituitary resistance
   
   Normally, circulating thyroid hormone prevents the hypothalamus and pituitary from calling for unnecessary thyroid hormone, similar to the way a warm room prevents a thermostat from releasing more heat into the room. Sometimes the pituitary does not respond to the stimulation it receives from thyroid hormones and continues to release more TSH to the thyroid gland. More thyroid hormone is released which causes the signs and symptoms associated with hyperthyroidism.
   
   
4. Toxic adenoma
   
   This is a type of tumor that is an abnormal extension of the thyroid gland which releases excess thyroid hormone. This tumor does not need releaser hormone from the pituitary so it continuously releases thyroid hormone on its own.
   
   
5. Multinodular goiters
   
   Multinodular goiter disease, the second most common cause of hyperthyroidism, is characterized by soft nodules that grow slowly within the thyroid. They can produce thyroid hormone on their own to cause signs and symptoms of hyperthyroidism. Multinodular goiters are often asymptomatic, however, they can grow large and compress the windpipe to cause difficulty breathing or swallowing.
   
   
6. Inflammatory thyroid disease
   
   Sometimes the thyroid can become inflamed, usually from a virus or occasionally after childbirth. Inflammation from a virus usually is painful and lasts from two to six months. The cause following pregnancy is poorly understood and can reoccur with subsequent pregnancies.
   
   
7. Ectopic thyroid tissue
   
   Other tissues and organs of the body can abnormally produce another source of thyroid hormone. Examples are tumors in the ovaries and follicular cancer.
   
   
8. Medication
   
   Hypothyroid patients that are overtreated with thyroid medication can actually become hyperthyroid and display signs and symptoms of excess thyroid hormone. About 2% of patients on amiodarone will become hyperthyroid due to the drug's high concentration of iodine (37% by weight) in its molecular structure. This, through a number of steps, can ultimately cause an increased release of thyroid hormone into the blood stream.