Goiter (also spelled goitre) refers to any visible enlargement of the thyroid gland.
The thyroid gland sits astride the trachea (windpipe) and is shaped like a butterfly. It makes thyroxin, a hormone that regulates the metabolic activity of the body, rather like the gas pedal regulates the action of a car. Too much thyroxin increases the metabolism, causing weight loss, temperature elevation, nervousness, and irritability. Too little thyroxin slows the metabolism down, deepens the voice, causes weight gain and water retention, and retards growth and mental development in children. Both conditions also alter hair and skin growth, bowel function, and menstrual flow.
Curiously, the thyroid gland is often enlarged whether it is making too much hormone, too little, or sometimes even when it is functioning normally. The thyroid is controlled by the pituitary gland, which secretes thyroid-stimulating hormone (TSH) in response to the amount of thyroxin it finds in the blood. TSH increases the amount of thyroxin secreted by the thyroid and also causes the thyroid gland to grow.
Historically, goiter was widespread and busts of Cleopatra suggest that she may have suffered from the condition. The availability of table salt to which iodine has been added has greatly reduced the prevalence of goiter in most developed countries. In North America, the frequency of goiter cases has been estimated at less than 5%. That number is much larger in countries where iodized salt is not available. The rates of goiter in the population in those countries, such as Russia, India, and Central and South African nations may exceed 50%.
Excess TSH (or similar hormones), cysts, and tumors will enlarge the thyroid gland. Of these, TSH enlarges the entire gland whereas cysts and tumors enlarge only a part of it.
The only symptom from a goiter is the large swelling just above the collar bone. Rarely, it may constrict the trachea (windpipe) or esophagus and cause difficulty breathing or swallowing or cause choking while eating. The rest of the symptoms come from thyroxin or the lack of it.
The size, shape, and texture of the thyroid gland help the physician determine the cause. A battery of blood tests is required to verify the specific thyroid disease. Functional imaging studies using radioactive iodine determine how active the gland is and what it looks like.
Goiters of all types will regress with treatment of the underlying condition. Dietary iodine may be all that is needed. However, if an iodine deficient thyroid that has grown in size to accommodate its deficiency is suddenly supplied an adequate amount of iodine, it could suddenly make large amounts of thyroxin and cause a thyroid storm, the equivalent of racing a car motor at top speed.
Hyperthyroidism can be treated with medications, therapeutic doses of radioactive iodine, or surgical reduction. Surgery is much less common now than it used to be because of progress in drugs and radiotherapy.
Although goiters diminish in size, the thyroid may not return to normal. Sometimes thyroid function does not return after treatment, but thyroxin is easy to take as a pill.
Euthyroid goiter and hypothyroid goiter are common around the world because many regions have inadequate dietary iodine, including some places in the United States. International relief groups provide iodized salt to many of these populations. Because mental retardation is a common result of hypothyroidism in children, this is an extremely important project.
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International Council for the Control of Iodine Deficiency Disorders, PO Box 51030, 375 des Epinettes, Ottawa ON, Canada, K1E 3E0, http://www.iccidd.org .
J. Ricker Polsdorfer, MD