Prevalence of islet cell antibodies and its correlation with glucose and insulin response to oral glucose tolerance test in 1st degree relatives of insulin dependent diabetes mellitus probands.

93 first degree relatives (1st DR) of insulin dependent diabetes mellitus (IDDM) patients were investigated for detection of islet cell antibodies (ICA) and beta cell functional status. ICA were detected in 26.9% Ist DR subjects (25/93), equally in parents, siblings and offspring. Normal (n = 16), impaired (n = 5) and diabetic (n = 4), glucose curves were seen in 1st DR. Low insulin levels were observed in parents and siblings with normal glucose tolerance test (N-GTT) at 90 min (p < 0.05), and (p < 0.0005) relatives with impaired glucose tolerance and diabetes. Insulin release to glucose (IRG-insulinogenic index) in control group was 352 +/- 42 mu U/mg. From the group of 25 ICA positive cases, 4 had mean IRG of 394 +/- 70 mu U/mg (group A) comparable to control, and had N-GTT; 12 had mean IRG of 107 +/- 15.9 mu U/mg (group B) significantly low (P < 0.005) compared to controls and group A and 9 showed IRG of 75 +/- 29.3 mu U/mg, lower than group B (NS) with abnormal response to glucose load. Loss of insulin secretory ability thus can precede hyperglycemia by years. The ICA positive relatives were grouped based on the immunological status with their probands. ICA status in probands does not give an idea about ICA status in their relatives. This indepth study leads to understand the correlation of genetic, metabolic and immunological parameters for early detection of IDDM in first degree relatives.