From the 1920's to the early 1970's, radiation was used to shrink enlarged thymus glands, tonsils and adenoids, to clear up birth marks and to treat acne and ringworm of the scalp. Several million children in the U.S. received head and neck radiation with external radiation or radium applicators. Initial indications of problems arose in the late 1950's and this treatment was largely abandoned during the 1960's. It was found to increase the risk of thyroid tumors, including thyroid cancer. Later, it was found that it increased the risk of other tumors. It is possible, but not certain, that the treatment affects the functioning of the thyroid gland as well.
If you were one of these children, it is a good idea to find out as much as you can about the specifics of your treatment, what it was for and how much radiation you received and where. The medical records department of the hospital where you were treated can sometimes tell you about the dose and number of treatments, particularly if you can supply the dates and the name of the doctor who prescribed it.
What kinds of risks are we talking about? Your chances of developing tumors and cancer at some time in your life are higher than if you never had the radiation exposure. The amount by which your risk increases depends on how much radiation you received and your age when it occurred. The younger you were, the greater the risk. As an example, the risk over your lifetime of developing thyroid cancer would be several fold greater than usual if you were exposed to a large amount of radiation at an especially young age.
A person who has been exposed to radiation is more likely to develop thyroid nodules and those nodules have a greater chance of being cancerous. This is why your doctor will probably want to biopsy any nodule you develop, in order to exclude cancer.
There are other important organs in your neck that can react in later years to the childhood irradiation. The parotid glands (the "mumps" glands below your ears) can develop tumors. The parathyroid glands located next to the thyroid may also develop tumors leading to problems with calcium regulation and bone loss. Also, benign tumors in the nervous system may develop. One common type affects hearing and balance.
What should you do? If you find out that you did have childhood radiation to your head and neck, you should make sure that your doctor is aware of this extra risk in your background. Above all make sure a thyroid and neck exam are part of your yearly physical examination.