ENDEMIC (IODINE-DEFICIENT) GOITER
The most common type of goiter, encountered chiefly in geo-graphic regions where the natural supply of iodine is deficient (eg, the Great Lakes areas of the United States), is the so-called sim-ple or colloid goiter. In addition to being caused by an iodine de-ficiency, simple goiter may be caused by an intake of large quantities of goitrogenic substances in patients with unusually susceptible glands. These substances include excessive amounts of iodine or lithium, which is used in treating bipolar disorders.
Simple goiter represents a compensatory hypertrophy of the thyroid gland, caused by stimulation by the pituitary gland. The pituitary gland produces thyrotropin or TSH, a hormone that controls the release of thyroid hormone from the thyroid gland. Its production increases if there is subnormal thyroid activity, as when insufficient iodine is available for production of the thyroid hormone. Such goiters usually cause no symptoms, except for the swelling in the neck, which may result in tracheal compression when excessive.
Many goiters of this type recede after iodine imbalance is cor-rected. Supplementary iodine, such as SSKI, is prescribed to sup-press the pituitaryâ€™s thyroid-stimulating activity. When surgery is recommended, the risk for postoperative complications is mini-mized by ensuring a preoperative euthyroid state by treatment with antithyroid medications and iodide to reduce the size and vascularity of the goiter.
Providing children in iodine-poor regions with iodine com-pounds can prevent simple or endemic goiter. If the mean iodine intake is less than 40 fg/day, the thyroid gland hypertrophies. The World Health Organization recommends that salt be iodized to a concentration of 1 part in 100,000, which is adequate for the pre-vention of endemic goiter. In the United States, salt is iodized to 1 part in 10,000. The introduction of iodized salt has been the sin-gle most effective means of preventing goiter in at-risk populations.