Toxic diffuse goiter, is an abnormal enlargement of the thyroid gland. Normally, the thyroid gland produces two major hormones, thyroxine and triiodothyronine, which circulate in the bloodstream and help regulate metabolism, help control body temperature, influence heart rate, and help regulate protein production. The normal functioning of the thyroid gland can be affected when the following disorders occur: 1. Iodine deficiency. People who live inland or at high altitudes tend to be iodine-deficient and can develop goiter when the thyroid gland enlarges to get more iodine.2. Graves’ disease. Goiter sometimes occurs when the thyroid gland produces too much thyroid hormone.3. Pregnancy. The hormone, human chorionic gonadotropin, produced during pregnancy may cause a slight enlargement of the thyroid gland. Goiter caused by other diseases such as hypothyroidism or hyperthyroidism can be accompanied by a variety of symptoms, such as lethargy, loss of appetite, and insomnia.