SCHNELLER HOMOLOGER RADIOIMMUNOASSAY FUR HUMAN-PARATHORMON (hPTH) ZUR DIFFERENZIERUNG DER HYPERKALZAMISCHEN KRISE

A rapid radioimmunoassay is described for parathyroid hormone as a diagnostic aid in hypercalcemic crisis. The antiserum was produced in goats against extracted human PTH, the working dilution of the antiserum being 1:4000. As a standard, synthetic human PTH fragment (53-84) is used, as tracer ¹²⁵I-(Tyr⁵²)-hPTH (52-84) labelled with the chloramine T-technique and separated from non-incorporated iodine on SEP-PAK C₁₈ cartridges. The incubation consists of a single step at room temperature, and separation of the bound and free fraction is effected by a mixture of second antibody and polyethylene glycol solution. Total assay time is 3 hours. The PTH levels found in 36 healthy normals were 10-30 pmol/l, elevated levels being found in 36 patients with primary and 19 patients with secondary hyperparathyroidism. In 10 of 13 patients with hypercalcemia of malignancy PTH was normal; the remaining patients had impaired renal function and PTH levels up to 70 pmol/l. In patients with hypercalcemic crisis caused by primary hyperparathyroidism, PTH levels were above 100 pmol/l. In cases of hypercalcemic crisis, reliable discrimination is achieved between primary hyperparathyroidism and other causes of hypercalcemia to warrant the use of such a 'rapid assay'.