What is the cause of an underactive thyroid gland?

With Hashimoto's, your body produces antibodies that attack and destroy the thyroid gland. Thyroiditis may also be caused by a viral infection. Other causes of hypothyroidism include: Radiation therapy to the neck area. read more

The most common cause of hypothyroidism is Hashimoto's thyroiditis. "Thyroiditis" is an inflammation of the thyroid gland. Hashimoto's thyroiditis is an autoimmune disorder. With Hashimoto’s, your body produces antibodies that attack and destroy the thyroid gland. Thyroiditis may also be caused by a viral infection. read more

Causes. An underactive thyroid (hypothyroidism) is when your thyroid gland doesn't produce enough of the hormone thyroxine (also called T4). Most cases of an underactive thyroid are caused by the immune system attacking the thyroid gland and damaging it, or by damage that occurs as a result of treatments for thyroid cancer or an overactive thyroid. read more

When a portion of the thyroid gland is surgically removed (eg, patients with thyroid nodules, thyroid cancer, Graves’ disease), this causes the remaining thyroid tissue to stop working properly—and may result in hypothyroidism. read more