Normocalcemia with elevated parathyroid hormone levels after surgical treatment of primary hyperparathyroidism.

BACKGROUND

Thirty percent of patients who undergo successful parathyroidectomy for primary hyperparathyroidism show unexplained elevated postoperative serum parathyroid hormone (PTH) levels despite normocalcemia.

METHODS

PTH levels were measured monthly in 97 patients for 6 months after parathyroidectomy. Renal function, 25-OH-vitamin D levels, serum alkaline phosphatase levels, osteocalcin, and bone densitometry were evaluated before and 6 months after surgery. PTH reactivity to calcium loading was tested at the sixth month.

RESULTS

Thirty patients had elevated PTH levels despite normocalcemia after parathyroidectomy. Before surgery, these 30 patients had higher PTH and creatinine levels, lower vitamin D levels, and more extensive bone involvement than those with normal postoperative PTH levels. In patients with normal renal function and normal vitamin D levels, postoperative PTH values correlated with preoperative PTH levels but not with bone disease.

CONCLUSION

In most cases, elevated PTH levels after surgery is an adaptive reaction to renal dysfunction or vitamin D deficiency. If no adaptive cause can be found, persistent hyperparathyroidism must be suspected.