Abstract: The authors report three cases of primary hyperparathyroidism (HPT) in patients with differentiated thyroid carcinoma (DTC) developed a few years after initial surgical and radiometabolic treatment of DTC. The early diagnosis of HPT in these patients was made possible because of laboratory tests performed during follow-up, including the assay of serum calcium and serum phosphorus levels. Scinti-graphy using 99mTc-MIBI enabled the correct preoperative localisation of a single parathyroid adenoma in two of these patients and multiglandular pathology in the third
