GOITRE

enlargement of the human thyroid gland, resulting in a prominent swelling at the front of the neck. A normal human thyroid gland weighs 2030 g (about 0.75 ounce), a goitrous gland as much as 1 kg (more than 2 pounds). A very large or extensive goitre may produce sensations of choking and can cause difficulty in breathing and swallowing. There are several causes and types of goitre. One class of goitre arises as a result of any of a variety of defects in the thyroid gland's synthesis of thyroid hormone. The gland is unable to secrete sufficient amounts of that hormone and grows larger as if to compensate for its inadequate secretion by producing more. Other types of goitre occur when the thyroid gland has normally functioning tissue but enlarges for reasons that have not been conclusively determined. Still another type of enlarged gland produces too much hormone (hyperthyroidism), resulting in the conditions known as exophthalmic goitre, or Graves' disease (q.v.), and toxic multinodular goitre, or Plummer's disease (q.v.). The most common type of goitre is called simple, or endemic, goitre and results from an inadequate intake of iodine, which is one of the two raw materials necessary to make thyroid hormone. When the body does not receive iodine in sufficient quantities, the thyroid gland grows larger in an effort to produce an adequate amount of hormone. Endemic goitre is five times more common among women than among men. It occurs most frequently in inland or mountainous regions where the iodine content of the drinking water and the food is exceedingly low. It is prevented by the use of iodized salt in one's diet. In the early stages of endemic goitre, regression of the gland may be complete if iodine is ingested in adequate amounts. The most effective treatment in more advanced cases is the administration of thyroid hormone. Surgical removal of the thyroid gland may be necessary if the gland has grown so large that it is obstructing breathing.