A prospective study of hyperparathyroidism in individuals exposed to radiation in childhood.

To determine the effects of childhood irradiation on the parathyroid glands, a cohort of 4297 patients who received radiation to the tonsils before the age of 16 years has been followed-up prospectively. Among the 2923 patients who were located and provided information, 32 patients developed clinical hyperparathyroidism. The incidence of clinical hyperparathyroidism was 18.7 per 100,000 person-years below the age of 40 years and 171 per 100,000 person-years in the age range of 40 to 60 years. This represents a 2.9-fold (95% confidence interval, 1.6 to 4.3) and 2.5-fold (95% confidence interval, 1.1 to 3.9) increase in the incidence of hyperparathyroidism compared with that among the general population. In addition, 31% of the patients who developed hyperparathyroidism also developed thyroid cancer, which is higher than the 11.2% prevalence of thyroid cancer in the patients who received radiation therapy who did not develop parathyroid tumors. Patients with a history of head and neck irradiation should have their parathyroid glands evaluated on a regular basis.