Prior irradiation and the development of coexistent differentiated thyroid cancer and hyperparathyroidism.

Twelve patients with coexistent well-differentiated thyroid carcinoma and primary hyperparathyoidism were studied to determine the frequency of previous radiation exposure. Eight were found to have received prior irradiation. External radiation was administered to the head and neck region for benign conditions such as tonsillar enlargement, acne, scrofula, and thyroid enlargement. One patient received 131I therapy for carcinoma of the thyroid. The observation that 67% of the patients in this series had previous radiation to the head and neck strongly implicates radiation exposure in the development of coexistent well-differentiated thyroid carcinoma and hyperparathyroidism.