Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland fails to function adequately, resulting in reduced levels of thyroid hormone in the body. Cretinism is a type of hypothyroidism that occurs at birth and results in stunted physical growth and mental development. Severe hypothyroidism is called myxedema.
There are many causes of hypothyroidism. Hashimoto’s thyroiditis is an autoimmune disease of the thyroid gland and the second most common cause of hypothyroidism. The most common cause of hypothyroidism is medical treatment, such as surgery or radiation to the thyroid gland, to treat hyperthyroidism (over-activity of the thyroid gland). Some drugs, such as lithium and phenylbutazone, may also induce hypothyroidism. Extreme iodine deficiency, which is rare in the United States, is another possible cause. Failure of the pituitary gland or hypothalamus to stimulate the thyroid gland properly can cause a condition known as secondary hypothyroidism.
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