Objective：To discuss the mechanism of  elevated postoperative serum parathyroid hormone (PTH) levels with normocalcemia in patients who undergoing successful parathyroidectomy for primary hyperparathyroidism.
Methods：PTH levels were measured in 97 patients 6 months after parathyroidectomy. The 25-OH-vitamin D levels, serum alkaline phosphatase levels, osteocalcin and bone densitometry were evaluated before operation and 6 months after surgery. PTH reactivity to calcium loading was tested six months postoperatively.
Results：Thirty patients had elevated PTH levels with normocalcemia after parathyroidectomy. Before surgery, these patients had higher PTH and creatinine levels, lower vitamin D levels, and more extensive change of bone than those with normal postoperative PTH levels. There were 67 patients whose PTH was normal after surgery with normal renal function and vitamin D levels, and without change in bones condition.
Conclusions：The elevated PTH levels after surgery for primary hyperparathyroidism is an adaptive reaction to renal dysfunction or vitamin D deficiency.