Transient rise in intact parathyroid hormone concentration after surgery for primary hyperparathyroidism.

Two-site immunometric assays for determination of the level of intact parathyroid hormone (PTH) in serum have enabled detailed clinical studies of PTH secretion. Fifty-one patients with primary hyperparathyroidism were studied before surgery and 2 years after operation. PTH levels dropped to low values after operation. A rebound increase in PTH concentration occurred from 10 days to 3 months after surgery. Abnormally raised postoperative PTH concentrations were noted in 31 per cent of the patients, who had lower serum concentrations of ionized calcium (Ca2+) than the rest (P < 0.003). Before operation these patients had a more pronounced hyperparathyroidism than the others. At 2 years after surgery there was still a positive correlation between PTH concentrations before and after surgery (P < 0.001). The rebound increase in the level of PTH was a general phenomenon probably caused by low Ca2+ concentrations at the time of remineralization of bone. This phenomenon was transient. The positive correlation between preoperative and postoperative PTH concentrations shows that effects of hyperparathyroidism can remain for a long time after surgical cure.