Coexistent parathyroid adenomas and thyroid carcinoma. Can radiation be blamed?

The coexistence of parathyroid adenomas and thyroid cancer in a substantial number of patients with primary hyperparathyroidism has led to speculation implicating ionizing radiation as a possible cause. Experience with a group of 40 individuals harboring both tumors was reviewed and evidence of roentgen ray exposure to the head and neck was found in only one of these patients. Association of parathyroid adenomas and thyroid carcinoma cannot be explained on the basis of prior irradiation to the neck.