[Epidemiological research on primary hyperparathyroidism. A prospective multicenter study].

Serum calcium determination of 11,588 hospitalized patients during a twelve-month period revealed hypercalcaemia in 74 (0.64%). Further clinical and biochemical investigation established primary hyperparathyroidism in 20 of them (27%), and in 15 (20%) a malignant tumour (with bone metastases in six) as the cause of the hypercalcaemia. Rarer causes were found in 11 patients (15%): diuretic medication (5), lithium treatment (3), immobilization (2) or hyperthyroidism (1). In the remaining 28 patients (38%) no cause of the hypercalcaemia could be established with certainty. In at least six patients, however, there were clinical pointers towards hyperparathyroidism in the absence of unequivocal biochemical findings. Leaving out of account borderline cases, one must reckon on a prevalence of hyperparathyroidism in 0.17% of an unselected group of hospitalized patients. Parathyroid hyperfunction must always be considered in the differential diagnosis because of its manifold clinical presentation.