Ashrafian, Hasan

Hypothyroidism, also called&nbsp;underactive thyroid&nbsp;or&nbsp;low thyroid, is a&nbsp;disorder of the endocrine system&nbsp;in which the&nbsp;thyroid gland&nbsp;does not produce enough&nbsp;thyroid hormone.&nbsp;It can cause a number of symptoms, such as&nbsp;poor ability to tolerate cold, a&nbsp;feeling of tiredness,&nbsp;constipation,&nbsp;depression, and&nbsp;weight gain.&nbsp;Occasionally there may be swelling of the front part of the neck due to&nbsp;goiter.&nbsp;Untreated cases of hypothyroidism during&nbsp;pregnancy&nbsp;can lead to delays in&nbsp;growth and intellectual development&nbsp;in the baby or&nbsp;congenital iodine deficiency syndrome.<br /> Worldwide,&nbsp;too little iodine&nbsp;in the diet is the most common cause of hypothyroidism.&nbsp;Hashimoto's thyroiditis&nbsp;is the most common cause of hypothyroidism in countries with sufficient dietary iodine.&nbsp;Less common causes include previous treatment with&nbsp;radioactive iodine, injury to the&nbsp;hypothalamus&nbsp;or the&nbsp;anterior pituitary&nbsp;gland, certain medications,&nbsp;a lack of a functioning thyroid at birth, or previous&nbsp;thyroid surgery.&nbsp;The diagnosis of hypothyroidism, when suspected, can be confirmed with&nbsp;blood tests&nbsp;measuring&nbsp;thyroid-stimulating hormone&nbsp;(TSH) and&nbsp;thyroxine&nbsp;levels.