Correlation of intraoperative parathyroid hormone levels with parathyroid gland size

OBJECTIVES: To study the relationship of intraoperative intact parathyroid hormone levels (iPTH) with parathyroid adenoma weight and volume in patients with primary hyperparathyroidism. METHODS: Retrospective evaluation of consecutive patients undergoing minimally invasive parathyroidectomy with iPTH measurement. Data collected include preoperative serum calcium, ionized calcium, and serum parathyroid hormone (PTH) levels, iPTH levels at baseline, 5 minutes, and 10 minutes, and parathyroid adenoma weight. Adenoma volume was calculated using an equation for the volume of a spheroid object. RESULTS: Thirty patients underwent minimally invasive parathyroidectomy with iPTH measurement for a single parathyroid adenoma between March 2004 and January 2006. There were 8 men and 22 women, with a mean age of 59.3 (range 26-92) years. A significant correlation between preoperative serum calcium and ionized calcium levels and parathyroid adenoma weight was identified (P = .0008 and P = .03, respectively). A significant correlation was also shown between baseline iPTH measurements and parathyroid adenoma volume (P = .03). There was no correlation between baseline iPTH levels and parathyroid adenoma weight. There was a significant correlation between parathyroid adenoma weight and percentage decrease of iPTH levels at 10 minutes compared to baseline (P = .04). CONCLUSION: Preoperative serum calcium and baseline iPTH levels may be useful in predicting parathyroid adenoma weight and volume, respectively. Adenoma weight may relate to the percentage decrease of iPTH levels at the 10-minute postparathyroidectomy interval.