Endogenous insulin can be detected in the plasma of untreated classic juvenile diabetics in the fasting state, and the fasting plasma insulin concentrations are comparable with those found in nondiabetics. There is, however, no insulin secretory response after ingestion of glucose.1,2
After treatment for weeks or months with exogenous insulin, antibodies against insulin are always formed and circulate in the blood. These antibodies make the estimation of the endogenous plasma insulin concentration impossible using the common immunological methods.
We have recently had the opportunity to study a patient who had both insulin-requiring classic juvenile diabetes and acquired hypogammaglobulinemia. He has now been treated for ten years with insulin, but because of the hypogammaglobulinemia, no humoral antibodies could be detected in his plasma. It was thus possible to investigate the endogenous insulin concentration in a patient with classic juvenile diabetes of ten years' duration and to try to ascertain whether