Persistent elevated serum levels of intact parathyroid hormone after operation for sporadic parathyroid adenoma: Evidence of detrimental effects of severe parathyroid disease

Abstract

A significant number of patients with primary hyperparathyroidism (pHPT) who are surgically treated have increased serum levels of intact parathyroid hormone (PTH) during long-term follow-up despite normocalcemia. The cause and significance of this finding remain to be established. A total of 82 patients operated on for sporadic parathyroid adenoma were investigated before and at 8 weeks and 1 year after operation with serum levels of intact PTH, bone mineral content, and biochemical variables known to reflect PTH activity. All patients had low or normal serum levels of calcium during follow-up. At 8 weeks after operation 20 (24%) patients had increased serum levels of PTH. These patients had severe parathyroid disease and low levels of 25(OH) vitamin D before operation. In contrast to patients with normal levels of PTH after operation, they did not have an elevated bone mineral content but had elevated levels of serum creatinin. At 1 year after operation 13 patients had elevated serum levels of PTH. Compared with patients with normal serum levels of PTH, they were older and had an increased frequency of cardiovascular disease and biochemical indications of compromised renal function. They did not have an elevated bone mineral content. Persistently increased serum levels of PTH indicate harmful effects of pHPT even after surgical cure, especially in elderly patients with severe disease before operation. The results in this investigation therefore favor early treatment of pHPT.