The development of a two-site enzyme immunometric assay (EIA) for calcitonin and its application in the measurement of the hormone in normal subjects, MTC-patients and post-menopausal women.

: We have developed a sensitive, two-site enzyme immunometric assay (EIA) using high affinity monoclonal antibodies for the measurement of immunoreactive human calcitonin (i-hCT) and compared the performance of the assay with that of the conventional radioimmunoassay (RIA). The sensitivity of an overnight EIA (2 pmol/l) was comparable with the long incubation (7 days) RIA. Both, the EIA and the RIA have been applied for the measurement of i-hCT in three groups: normal volunteers (n = 53), post-menopausal women (n = 25) and patients with MTC (n = 20). The results showed that in all three groups, the level of i-hCT was somewhat lower than that measured by RIA due to its greater specificity. The EIA can provide an attractive alternative to the conventional RIA for both routine diagnostic work and physiological studies.