Hypothyroidism is due to a problem in the thyroid gland itself and is called primary hypothyroidism. However, certain medications and diseases can also decrease thyroid function.

The causes of hypothyroidism include the following conditions:

• Iodine deficiency or exposure to Iodine-131 (I-131) can increase that risk.

• Neck surgery

• Thyroid surgery

• Sporadic inheritance

• Adequate iodine intake

• Autoimmune Thyroiditis (called as Hashimoto's thyroiditis) - a form of thyroid inflammation caused by the patient's own immune system

• Drug induced Hypothyroidism - Taking some prescription medications may alter thyroid function

• Medical treatments - Treatment of hyperthyroidism with radioactive iodine also results in destruction of thyroid tissue and may lead to hypothyroidism

• DiGeorge's syndrome