Purpose: Intraoperative parathyroid hormone (ioPTH) measurement has facilitated a move to minimally invasive parathyroidectomy. Patients are referred for surgery earlier with milder hypercalcaemia and smaller tumours. Whilst previous research has shown that glands size can affect ioPTH kinetics in patients with multiple gland disease, the dynamics of ioPTH in patients with mild hyperparathyroidism (HPT) has not been studied. We therefore investigated the relationship between biochemical parameters and parathyroid adenoma weight, and determined the dynamics and accuracy of ioPTH assay in patients with milder hypercalcaemia undergoing parathyroidectomy.
Methods: Patients undergoing parathyroidectomy for single gland disease from January 2004 to March 2011 were divided prospectively into two groups according to preoperative serum calcium: patients with a preoperative calcium ≥ 2.85 mmol/L (11.4 mg/dL) and <2.85 mmol/L were grouped as severe and mild hypercalcaemia, respectively. Correlation coefficients were calculated to assess the relationship between biochemical markers of calcium homeostasis and ioPTH measurements with respect to parathyroid gland weight.
Results: There was a weak correlation of preoperative serum calcium (r = 0.248, r = 0.207), PTH (r = 0.392, r = 0.275), and baseline ioPTH (r = 0.516, r = 0.244) with parathyroid gland weight in severe (n = 113) and mild groups (n = 190), respectively. No correlation between the magnitude in ioPTH drop with parathyroid gland weight at 5 or 10 min post-excision for either group was observed. Success rates (post-operative normocalcaemia) were similar for each group (99.1 % severe, 98.9 % mild).
Conclusion: This prospective study provides evidence that ioPTH assay is a valuable tool in predicting adequate tissue removal in patients with milder and more severe hypercalcaemia due to single gland primary HPT.