The coming of age of radiation-induced hyperparathyroidism: Evolving patterns of thyroid and parathyroid disease after head and neck irradiation

This study investigates the association of thyroid and parathyroid disease in radiation-exposed patients and tests the hypothesis that hyperparathyroidism (HPT) occurs after a longer latency period. Routine questioning identified 40 patients in the endocrine surgery clinic with a history of radiation exposure. Patients with thyroid disease were screened for HPT and vice versa. The known diagnosis at initial referral was thyroid disease alone in 26 of 40 patients, HPT alone in 9 of 40 patients, and both in 5 of 40 patients. After screening was completed, a total of 18 of 40 patients were found to have both thyroid disease and HPT. HPT manifested an average of 17 years later than thyroid disease (52.6 ± 10.0 years vs 35.5 ± 13.8 years after radiation therapy [P <. 05]). One third of the patients with HPT had normal serum calcium levels despite elevated parathyroid hormone levels and abnormal parathyroid glands. As the widespread use of x-ray therapy for benign childhood conditions becomes more remote, practitioners should expect a decreasing number of patients with radiation-associated thyroid disease, with an increase in HPT. Patients with radiation exposure and thyroid disease should be evaluated carefully and followed for HPT. Those patients who undergo surgical procedures should have close inspection of the parathyroid glands, with biopsy and excision when appropriate.