Reelevation of parathyroid hormone level after parathyroidectomy in patients with primary hyperparathyroidism: importance of decreased renal parathyroid hormone sensitivity

BACKGROUND: We hypothesized that impaired peripheral sensitivity to parathyroid hormone (PTH) may play a role in reelevation of PTH after successful operation for primary hyperparathyroidism (pHPT). METHODS: Factors affecting reelevation of PTH were determined in 90 patients who underwent parathyroidectomy for pHPT. PTH/nephrogenous cyclic adenosine monophosphate ratio, as an index of renal resistance to PTH, was examined in relation to factors shown to influence reelevation of PTH. RESULTS: Serum PTH levels were elevated above the upper limit of normal in 23 patients (26%) at 1 week and in 39 patients (43%) at 1 month after parathyroidectomy. These 39 normocalcemic patients with elevated serum PTH at 1 month after parathyroidectomy had a higher preoperative serum level of PTH and lower serum phosphate and 25-hydroxyvitamin D (25OHD) concentrations than those with normal PTH (n = 59). Elevated PTH and low 25OHD were shown by multivariate analysis to be significant predictors of reelevation of PTH. Renal resistance to PTH was higher in patients with vitamin D deficiency or renal insufficiency than in patients with normal serum vitamin D concentrations or normal renal function, and it increased according to increases in levels of PTH. CONCLUSIONS: The mechanism of PTH reelevation in patients with pHPT after successful parathyroidectomy appears to be renal resistance to PTH.