Primary hypothyroidism develops when damage to the thyroid gland reduces its ability to produce T3 and T4. It is the most common type of hypothyroidism, occurring in over 99% of all people with ...

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 ...

Primary hypothyroidism is a more common form of hypothyroidism. ... Secondary hypothyroidism occurs when the thyroid gland functions correctly but the pituitary gland or hypothalamus does not.

It can be either primary or secondary. Primary hypothyroidism occurs when the functioning of the thyroid gland is affected by autoimmunity or medical interventions (e.g. surgery, radiation).