[Normocalcemic nephrolithiasis and primary hyperparathyroidism]

In normocalciuric and in hypercalciuric renal stone formers tubular calcium reabsorption (TRCa) was studied before and during an intravenous calcium infusion. In addition two patients with proven primary hyperparathyroidism (pHPT) were studied. TRCa was decreased in hypercalciuric stone formers whereas an increase was noted both in pHPT and in normocalciuric subjects. It is concluded that normocalciuric nephrolithiasis may be a manifestation of mild and/or early pHPT.