The most common cause of hypothyroidism in the United States is a condition called Hashimoto’s disease. Hashimoto’s disease, also called chronic lymphocytic thyroiditis, is a type of an autoimmune disease. Autoimmune diseases or disorders occur when the body’s immune system attacks the body’s normal tissues. In Hashimoto’s disease, the immune system creates antibodies that attack normal cells in the thyroid. As a result, the ability of the thyroid gland to produce thyroid hormone is impaired. Why the body’s immune system attacks normal cells and tissues is not fully clear.

Other causes of hypothyroidism may include the following:

Thyroiditis

Thyroiditis is a medical term used to denote inflammation of the thyroid gland. In this condition, stored thyroid hormone leaks out of the inflamed thyroid. Initially, the leakage of thyroid hormone raises their levels in the blood—a condition called hyperthyroidism—which can last for a month or two. However, most people develop hypothyroidism before the thyroid gland is completely healed.

Congenital Hypothyroidism

Congenital hypothyroidism occurs when a baby is born with a thyroid that is not functioning properly or is not fully developed. Early recognition of the disorder and prompt treatment is important to prevent complications, such as mental retardation and growth failure.

Surgical Removal of the Thyroid Gland

Hypothyroidism may also occur when a part or the entire thyroid has been surgically removed. When only a part of the thyroid is removed, the remaining thyroid cells may still produce normal amount thyroid hormone. However, some people may also develop hypothyroidism.

If the entire thyroid has been removed, hypothyroidism always occurs.

Radioiodine Therapy

Radioactive iodine, which is a common treatment for hyperthyroidism, can gradually destroy thyroid cells. Almost everyone who undergo radioiodine therapy eventually develops hypothyroidism.

Medications

Certain drugs such as amiodarone (a heart medication), interferon alpha (a cancer medication), and lithium (a bipolar disorder medication), can interfere with thyroid hormone production. (National Endocrine and Metabolic Diseases Information Service, May 2008) As a result, hypothyroidism occurs.

Page Last Revised: November 27, 2010

Top of Page