The causes of most types of thyroid disease remain largely unknown. A careful history will reveal a relative with a thyroid problem in approximately 50% of patients. Sometimes this may be a grandparent or an aunt so that it may seem to "skip" a generation. Various types of thyroid disease are sometimes seen in the same family. All types of thyroid disease are more common in women than in men.

Contrary to popular myth, the foods we eat, including seafood, are not related to thyroid disease. Although iodine deficiency was an important factor until the first part of this century, it is no longer felt to be related to thyroid disease in this country. A few areas of the world, such as Tibet, still have insufficient iodine in their diet that can lead to goiter. The iodine added to salt and found in our foods (milk and bread) has abolished this problem in our country and the rest of the Western World. Sometimes, too much iodine such as taking kelp tablets or in medicines used in x-ray of the kidney and gallbladder actually precipitate a thyroid problem. Today there is never a need for people in this country to take supplemental iodine! If you normally take vitamins, you should take only those that have no supplemental iodine.

One definite cause of thyroid disease has been found. Previous radiation to the head and neck during childhood causes an increase in thyroid disease. In the 1940's and 1950's many children and teenagers received radiation for acne, thymus gland enlargement, tonsillitis and adenoiditis. It was even used to remove birth marks and treat ring worm of the scalp. A high incidence of goiters developed in these people fifteen to thirty years later. Approximately 7% of patients who received this radiation developed thyroid cancer. Only radiation treatments, not diagnostic or dental x-rays have caused this problem. Radioactive iodine scans or treatment do not cause this problem! Children exposed to radioactive fallout in Chernobyl have developed a high rate of thyroid cancer. Studies are currently being done to see if this was a problem in the USA with the A bomb test in the 1950's.

Patients who know they received this treatment, even many years earlier, should be aware of the problem. Usually an initial thyroid scan is done on such patients and they are taught to self examine their thyroid gland every month and be checked by a physician each year. Since parathyroid disease is also increased in this group of patients, a serum calcium level is also checked each year.

Until recently, adults were thought to be immune to this radiation. However, now that many people with Hodgkin's Disease and other types of cancer who were treated with radiation are surviving over 20 years, we are now seeing hypothyroidism in this group of individuals. Fortunately, these adults have not shown an increase in thyroid cancer.