A Unique Form of Circulating Insulin in Human Islet Cell Carcinoma

We have partially characterized the circulating insulin components from a patient with islet cell carcinoma. The proinsulin-like component is larger in size, less reactive by radioimmunoassay, and more reactive by bioassay than identical preparations from a non-tumor patient. The insulin component is less reactive by radioimmunoassay but otherwise indistinguishable from the non-tumor component. These unique circulating insulin components either represent a specific mutation in an individual patient or a more general heterogeneity of the insulin components in disease states.