Conditions for a radioimmunoassay of serum parathyroid hormone.

A radioimmunoassay for parathyroid hormone is described that circumvents some previous difficulties. Parathyroid hormone binds strongly to other serum components. Consequently, a “control” curve is set up for each specimen, the specimen consisting of serum, diluent, and radiolabel, but no antibody. Final calculations are then based on the difference between the control curve and the curve obtained by incubating serum, diluent, radiolabel, and antibody. The lack of parallelism between various sample curves makes it almost mandatory that curves derived from at least 12 dilutions of serum be included for each specimen.