What causes thyroid problems?

Thyroid problems are caused by an underproduction or overproduction of the body's thyroid hormones. When the body doesn't produce enough of these hormones, hypothyroidism results, according to WebMD, and when the body produces too much thyroid hormones, hyperthyroidism results.

Hypothyroidism is caused by the autoimmune disorder Hashimoto's thyroiditis, which causes the body to attack its own thyroid tissue, according to WebMD. Hypothyroidism can also be caused by thyroid gland removal or exposure to excessive amounts of iodide or the drug lithium.

By contrast, hyperthyroidism is generally caused by Graves' disease, toxic adenomas or malfunctions of the pituitary gland. It can also be caused by an inflammation of the thyroid gland that is known as subacute thyroiditis, according to WebMD.