Immuno-heterogeneity of the calcitonins of hypercalcemia, breast and lung cancers and medullary carcinoma of thyroid.

Four antisera raised in the goat have very different properties: all recognized the immunoreactive calcitonin (iCT) of medullary carcinoma of the thyroid (MCT), one the response of normal subjects to induced or endogenous hypercalcemia and 2 others a different molecular species which occurs in half the patients with cancer of breast and 3/4 of patients with cancer of the lung. The latter two antisera are most sensitive to the 22-32 sequence of human calcitonin. Depending on the antiserum used, 4 or 7 peaks of immunoreactivity are found in eluates by column chromatography or stimulated serum from MCT. Not all elevated levels of iCT in serum are diagnostic of MCT and ectopic production by lung and breast cancer must be considered. Presence of higher levels of iCT with greater amounts of cancer tissue and undetectable levels after surgery or radiotherapy when using antisera which require intact molecule of calcitonin for recognition suggest the possibility that sequential calcitonin levels with differentiating antisera may be helpful in assessing the extent of disease and response to therapy.