What Is Hypothyroidism?

Hypothyroidism is a disease of thyroid hormone deficiency.

The most common cause of hypothyroidism worldwide is insufficient intake of iodine, a mineral found in iodized salt and some foods (such as seafood and dairy) that is needed for production of thyroid hormones. In the US and other high-income countries, the most common cause of hypothyroidism is an autoimmune condition called Hashimoto thyroiditis.1