The person can lose mental function and even go into a coma . Hypothyroidism is most commonly caused by an autoimmune disorder . An autoimmune disorder is a condition in which the body produces antibodies that attack its own cells for no known reason. Hashimoto's thyroiditis is an example of an autoimmune disorder that attacks the thyroid gland. Over time, this makes the thyroid gland unable to produce normal amounts of thyroid hormone.
Some individuals have an overactive thyroid, a condition known as hyperthyroidism .
Medications can be given to destroy a portion of an overactive thyroid. If too much medication is given, the person can develop low thyroid function, or hypothyroidism. Surgery to remove the thyroid gland in someone with a condition such as thyroid cancer can also cause hypothyroidism. There is no known way to prevent autoimmune disorders that cause hypothyroidism, such as Hashimoto's thyroiditis . Careful monitoring of medications used to treat an overactive thyroid can help prevent hypothyroidism caused by destruction of too much of the gland tissue.