PRIMARY HYPERPARATHYROIDISM WITH NORMAL I NTACT PARATHYROID-HORMONE LEVELS AND HISTOLOGICALLY DETECTED PARATHYROID ADENOMA

We report an 18-year old woman with surgically proven primary hyperpar athyroidism (pHPT) and normal intact parathyroid hormone (iPTH) serum levels. The reason for this rare biochemical presentation are possible biologically active amino-terminal parathyroid hormone polypeptide fr agments not detected by the widely used two-site immunoradiometric par athyroid hormone assay (PTH IRMA). Diagnosis and therapy of primary hy perparathyroidism therefore should not exclusively rest on the finding of hypercalcemia coupled with an elevated iPTH level.