Parathyroid hormone levels in thyroid-vein blood of patients without abnormalities of calcium metabolism.

Abstract

Five patients without disorders known to influence calcium metabolism were considered euparathyroid by standard laboratory tests and normal peripheral radioimmunoactive plasma parathyroid hormone levels. All five had higher concentrations of parathyroid hormone in the drainage from both sides of the thyroid venous bed, ranging from 1.9 to 20 times the peripheral concentration. Hyperplastic parathyroid glands cause similar bilateral local increases in concentration. In known cases of hyperparathyroidism bilateral thyroid venous hormone increases indicate hyperplasia. In equivocal cases with normal peripheral parathyroid hormone levels, however, such localized increases indicate the need for further investigation to ensure the diagnosis of hyperparathyroidism.