Persistently elevated parathyroid hormone levels after parathyroid surgery

Abstract

Persistent elevation of serum parathyroid hormone (PTH), despite normocalcemia, occurs in 8% to 40% of patients after parathyroidectomy. Explanations have included hypocalcemia owing to vitamin D deficiency or bone remineralization, and persistent hyperparathyroidism. A retrospective chart review of 816 consecutive patients who underwent surgery for primary hyperparathyroidism was conducted. One hundred fourteen patients (15%) had persistently elevated PTH levels (PPTH). Patients with PPTH had higher preoperative PTH levels than those with normal PTH levels postoperatively. They also had lower postoperative Ca(++) and vitamin D levels. Multiple gland enlargement was identified in fewer patients with PPTH than in those with normal postoperative PTH levels. In patients with PPTH and a postoperative Ca(++) less than 9.6 mg/dL (group I), there was a greater decrease in IOPTH, a higher initial postoperative PTH level, and a lower postoperative vitamin D level than in PPTH patients whose postoperative Ca(++) was > or =9.6 mg/dL (group II). Postoperative Ca(++) and vitamin D levels were also lower in patients whose PPTH did not ultimately resolve. Three patients in group II had recurrent disease. Persistent elevation of postoperative serum PTH levels in normocalcemic patients is associated with mild hypocalcemia, probably owing to vitamin D deficiency. In some patients it may also be indicative of mild persistent hyperparathyroidism.