Wikipedia:VideoWiki/Hypothyroidism

Definition
Hypothyroidism, also called underactive thyroid or low thyroid, is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. 100px|left

Symptoms
It can cause a number of symptoms, such as poor ability to tolerate cold, a feeling of tiredness, constipation, depression, and weight gain. 100px|left

Neck swelling
Occasionally there may be swelling of the front part of the neck due to goiter. 100px|left

Untreated effects during pregnancy
Untreated hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby or congenital iodine deficiency syndrome. 100px|left

Cause
Worldwide, too little iodine in the diet is the most common cause of hypothyroidism. 100px|left

Iodine
In countries with enough iodine in the diet, the most common cause of hypothyroidism is the autoimmune condition Hashimoto's thyroiditis. 100px|left

Infrequent causes
Less common causes include: previous treatment with radioactive iodine, injury to the hypothalamus or the anterior pituitary gland, certain medications, a lack of a functioning thyroid at birth, or previous thyroid surgery. 100px|left

Diagnosis
The diagnosis of hypothyroidism, when suspected, can be confirmed with blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine levels. People over the age of 60 are more commonly affected. 100px|left

Treatment
Salt iodization has prevented hypothyroidism in many populations. Hypothyroidism can be treated with levothyroxine. 100px|left

Adjusting dose
The dose is adjusted according to symptoms and normalization of the thyroxine and TSH levels. Thyroid medication is safe in pregnancy. 100px|left

Effect of excess iodine
While a certain amount of dietary iodine is important, excessive amounts can worsen certain types of hypothyroidism. 100px|left

Epidemiology
Worldwide about one billion people are estimated to be iodine deficient; however, it is unknown how often this results in hypothyroidism. 100px|left

Burden in the US
In the United States, hypothyroidism occurs in 0.3–0.4% of people. People over the age of 60 are more commonly affected. Hypothyroidism is more common in women than men. 100px|left

Subclinical hypothyroidism rate
Subclinical hypothyroidism, a milder form of hypothyroidism characterized by normal thyroxine levels and an elevated TSH level, is thought to occur in 4.3–8.5% of people in the United States. 100px|left

Other animals
Dogs are also known to develop hypothyroidism and in rare cases cats and horses. 100px|left

History
The word "hypothyroidism" is from Greek hypo- meaning "reduced",  thyreos for "shield", and eidos for "form". 100px|left