Preoperative parathyroid hormone levels are correlated with parathyroid adenoma volume and bone mineral density but not serum calcium levels

Aim. The aim of this study was to determine the relationship between biochemical parameters, parathyroid adenoma volume, and bone mineral density with respect to intact parathyroid hormone (iPTH) levels in patients with primary hyperparathyroidism. Methods. Data were collected retrospectively from patients with primary hyperparathyroidism who were diagnosed and followed in our clinic between 2005 and 2008. Forty-eight (female/male=42/6) patients with a mean age of 52.8 +/- 13.1 years were enrolled into the study. Results. Bone pain was the most common presenting feature, seen in 41.7% of patients, while 29.1% of patients were asymptomatic. The mean serum calcium and iPTH concentrations were 2.9 +/- 0.6 mmol/L and 657.1 +/- 682 ng/L, respectively. The mean total Z/T scores of dual-energy X-ray absorptiometry (DEXA) scan at the femur and lumbar spine were -0.4 +/- 1.6/-1.0 +/- 1.7 and -1.4 +/- 1.6/-2.2 +/- 1.5, respectively. Preoperative iPTH levels were correlated with serum phosphate (r=-0.412, P=0.005), alkaline phosphatase (r=0.698, P=0.0001), and femur (r=-0.402, P=0.020) and lumbar spine total Z scores (r=-0.441, P=0.013), whereas parathyroid adenoma volume was correlated with iPTH (r=0.367, P=0.036) and alkaline phosphatase (r=0.570, P=0.001). There was no correlation between iPTH, serum calcium levels and total T scores at the femur and lumbar spine. After excluding patients with 25-OHD insufficiency, there was still no correlation between serum iPTH and calcium levels. Parathyroid adenoma volume, serum iPTH and calcium levels were also not different between patients with and without 25-OHD insufficiency. Conclusion. These results suggest that serum iPTH level may be useful in predicting parathyroid adenoma volume and it is also well correlated with femur and lumbar spine Z scores.