Laboratory Tests in the Diagnosis of Hyperparathyroidism in Hypercalcemic Patients

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Abstract
The results of tests of serum phosphate concentration or urine Ca or phosphate excretion, either under controlled conditions or after infusion of Ca or phosphate, were examined for their value in diagnosing primary hyperparathyroid-ism (PHP). The results of these tests were compared in hypercalcemic patients with PHP, normal subjects, patients with renal stones, and patients with hypercalcemia caused by non-parathyroid tumors. Published data and personal experience demonstrate that these tests are all insensitive and nonspecific for the diagnosis of PHP. Patients with hypercalcemia should be examined for all possible causes of hypercalcemia, and when none can be identified, a diagnosis of PHP should be considered. Unfortunately, none of the tests discussed will confirm the diagnosis of PHP. The most difficult patients to identify are those with hypercalcemia caused by PHP and non-parathyroid malignant neoplasms without demonstrable bony metastases. In the latter patients the clinical and laboratory findings may be indistinguishable from those of patients with PHP. In patients in whom PHP is suspected, the decision whether or not to perform a parathyroid exploration should be based primarily on the signs, symptoms and prognosis of the particular patient rather than on the results of any of the tests analyzed in this report.