RE-EXAMINATION OF HUMAN CALCITONIN RADIOIMMUNOASSAY

Abstract

Evaluations of human immunoreactive calcitonin (IRCT) assay were extensively reviewed. Labeled hormone was re-purified on carboxymethylcellulose in order to isolate a fraction containing mainly monoiodinated calcitonin, which was very stable. Two antisera with different immunochemical characteristics were used for incubation studies, one of which was incubated with unextracted and extracted plasma samples. The sensitivity of the assays was 60 pg/ml plasma. However, marked differences were observed in the results obtained by the 3 methods depending on the importance of the inhibitory effect of plasma on the binding of the tracer to antibodies. However, the absolute plasma IRCT level could not be related to the presence of calcitonin M, except in 1 case. Further studies are needed in order to ascertain the origin and the significance of the immunoreactive material which was detected in normal plasma by 1 antiserum.