Patients with Elevated Serum Parathyroid Hormone Levels after Parathyroidectomy: Showing Signs of Decreased Peripheral Parathyroid Hormone Sensitivity

Abstract

We have previously shown that patients with elevated levels of parathyroid hormone (PTH) after surgery for parathyroid adenoma have normal parathyroid and renal function but demonstrate signs of remineralization of cortical bone, decreased calcium absorption, and low levels of vitamin D. We hypothesized that decreased peripheral PTH sensitivity could also be of importance for this condition. Thirteen patients operated on for a solitary parathyroid adenoma, with a mean ± SD preoperative serum level of calcium of 2.72 ± 0.12 mmol/L, were investigated 6 weeks after surgery with a standardized PTH (1-34) infusion test for 6 hours. The eight patients with elevated PTH levels had less increase in serum levels of ionized calcium (0.02 ± 0.03 mmol/L) than did the five patients with normal PTH levels (0.06 ± 0.02 mmol/L) (p < 0.05). Patients with elevated PTH also showed less decrease in serum phosphate levels (p < 0.05) and a trend to a larger decrease in the excretion of urinary calcium (p = 0.08). The increase in 1,25-dihydroxyvitamin D₃ did not differ between the two groups of patients. Thus patients operated on for parathyroid adenoma with postoperatively elevated serum PTH levels showed decreased peripheral sensitivity to PTH.