The relation of serum calcium and immunoparathormone levels to parathyroid size and weight in primary hyperparathyroidism.

This study was designed to determine whether the serum calcium or immunoparathormone (iPTH) level would be of value in predicting the size or weight of the parathyroid gland in patients with single-gland enlargement caused by primary hyperparathyroidism. Ninety-two patients who underwent parathyroidectomy with removal of a single enlarged gland at the North Carolina Memorial Hospital (1974 to 1984) were reviewed. The preoperative calcium and immunoparathormone levels were correlated to the weight and calculated volume of the removed gland. The calcium level was found to be significantly associated with parathyroid gland weight and volume (p less than 0.001), as determined by linear regression analysis. Despite the statistical association, the correlation coefficient (calculated with the Pearson correlation matrix) was low, 0.16 for the relation of calcium to gland weight and 0.25 for the relation of calcium to calculated gland volume. The calculated coefficients of correlation of iPTH (three different assays) to gland weight and volume were similarly low. These findings demonstrate a variable relationship between the preoperative serum calcium level or the iPTH level to the weight or volume of the enlarged hyperfunctioning parathyroid gland. Identification of the pathologic parathyroid gland(s) in primary hyperparathyroidism cannot be based on a perceived relation of preoperative calcium or iPTH levels to the size of the enlarged glands.