Due to the addition of iodine to table salt and iodine-laced disinfectants used on cows' udders, this cause of hypothyroidism has disappeared in the US .
Hypothyroidism is the most common thyroid disorder.
Severe hypothyroidism can lead to a condition called myxedema, characterized by dry, thickened skin and coarse facial features. One such autoimmune disorder is called Hashimoto's thyroiditis, an inflammation of the thyroid gland. Other causes include treatment of hyperthyroidism such as radioactive iodine treatment or surgery. Symptoms of hypothyroidism are usually very subtle and gradual and may be mistaken for symptoms of depression. The following are the most common symptoms of hypothyroidism.