PTH radioimmunoassay and loading tests in the diagnosis of patients with primary hyperparathyroidism.

PTH radioimmunoassay today represents an unreplaceable tool in the diagnosis of primary hyperparathyroidism. However, the diagnostic importance of its dosage on selective venous samples is still discussed. Herein, we report our experience of 47 patients operated on for primary hyperparathyroidism. The catheterization of neck veins was performed according to Doppman and co-workers. The PTH assay was carried out with COOH- and NH2-specific antisera. (In 5 cases an inhibition test with CaCl2 infusion was practiced during selective catheterization to preoperatively discriminate between adenoma and hyperplasia.) In 8 cases loading tests with EDTA and in 6 cases with CaCl2 were also performed in association with peripheral venous sampling, in an attempt to improve its sensibility. The 47 cases operated upon showed the following results: the peripheral PTH values were significantly raised in 60\% of the cases; the selective PTH dosage with COOH-specific antiserum showed a parathyroid hyperfunction in 100\% of the surgically confirmed cases, whereas with the NH2-specific antiserum an increased PTH rate was found only in 84\%. A right preoperative localization was obtained in 73\%. The value of loading tests is more difficult to evaluate and is discussed in detail.