PTH and malignant tumor of parathyroid gland: However, a recent study conducted by Zhang in 2019 demonstrated that parathyroid malignant tumors have a higher uptake level of Tc99-MIBI than benign tumors and the peak of retention index (RI peak, p < 0.001) in correlation to serum levels of parathyroid hormone (PTH) may contribute to a preoperative differential diagnosis of parathyroid carcinoma [20].