Goiter is a condition in which the thyroid gland becomes enlarged. The gland is located toward the front of the neck between the Adam’s apple and the top of the breastbone. In most cases, a goiter appears as a smooth swelling at the front of the neck.
In healthy individuals, the thyroid gland takes up iodine from the blood to form a hormone called thyroxine. This hormone regulates growth and metabolism, the process by which the body turns food into energy and living tissue. Another hormone, called thyroid-stimulating hormone (TSH), causes the thyroid to release the thyroxine. TSH is produced by the pituitary gland, which lies near the center of the skull.
Goiters develop because the thyroid gland is not active enough or because it is too active. When the thyroid is not active enough, the condition is called hypothyroidism. In this condition, the pituitary gland responds to the low level of thyroid activity by producing more TSH. This excess TSH causes the thyroid to swell. Patients suffering from hypothyroidism become physically and mentally sluggish. Their skin becomes thick and dry, and they may gain weight.
Hypothyroidism may have any of several causes. In the past, a lack of iodine in the diet led to many cases of hypothyroidism. However, the use of iodized salt has virtually eliminated this type of hypothyroidism in many developed countries. Hypothyroidism also may occur because of defects in the enzymes that produce the thyroxine. Another form of hypothyroidism develops when certain substances in the blood called antibodies attack the thyroid. Antibodies normally protect the body from infection.
When the thyroid is too active, a disorder called hyperthyroidism results. In this disorder, the thyroid cells produce too much thyroxine, and the thyroid may enlarge to form a goiter. Common symptoms of hyperthyroidism include nervousness, more rapid heartbeat, and weight loss. Another symptom is exophthalmos, a condition in which the eyeballs protrude.
Doctors treat goiter in a variety of ways, depending on its cause. For example, they may give pills containing small amounts of thyroxine to patients suffering from hypothyroidism. Doctors treat hyperthyroidism with drugs, surgery, or radioactive iodine, a form of iodine that slows down the thyroid’s activity. Exophthalmos is often seen when hyperthyroidism is caused by Graves’ disease. See Graves’ disease.
See also Congenital hypothyroidism; Iodine (Uses of iodine); Thyroid gland.
