Primary hypothyroidism develops when damage ... which healthcare professionals often use to describe either secondary or tertiary hypothyroidism. A 2017 review estimates that fewer than 1% of ...

Primary hypothyroidism occurs when the thyroid gland cannot produce enough thyroid hormones. Secondary hypothyroidism occurs when the thyroid gland functions correctly but the pituitary gland or ...

Primary hypothyroidism is about a thousand times more common than secondary and tertiary hypothyroidism. Some of the same conditions that cause hyperthyroidism can also cause hypothyroidism.