A linear regression model was used in the patient group to study the association of variables (BMI, age at diagnosis, age at primary operation, presence of persistent or recurrent PHPT at the time of DXA, presence of hypoparathyroidism, serum ionized and 24 h urinary calcium, PTH, plasma phosphate, alkaline phosphatase, 25-OH D, the number of operations for PHPT, and smoking), with BMD at all 3 locations. Here, PTH is linked to hypoparathyroidism.