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December 12, 2000

Diagnosis and Symptoms

Question from Crown Point, Indiana, USA:

Our son was diagnosed two years ago with type 1 diabetes. No antibody tests were performed at that time, but he presented with all the classic symptoms and a blood sugar of 240 mg/dl [13.3 mmol/L]. He was started on NPH and Humalog. During the first summer, his insulin needs were up to 7.5 units of NPH and 3 units of Humalog in the morning and 2 units of NPH and 2 units of Humalog in the evening. Over the last six months or so, his needs have decreased down to almost nothing. We just had him tested for GAD, islet cell antibodies and one other antibody, all of which were negative. He is only receiving 1unit of NPH in in the morning now, and his sugars have been good. He has a history of 126-150 mg/dl [7-8.3 mmol/L] fasting several times over the past two years and on occasion, spikes up to 200 mg/dl [11.1 mmol/L], though this is not often. We are bringing him for a second opinion, but I was just curious as to what what your team of experts make of this.

Answer:

As antibody testing has become more prevalent in the last few years, it has become clear that acute onset, insulin dependent diabetes in young people can be divided into two categories according to whether the antibody test is positive or not. The largest group are antibody positive and are now termed type 1A (autoimmune) and the remainder are called type 1B. Usually antibodies disappear in the two years after first diagnosis, but a negative test in your son’s case, where there had been a typical type 1 onset and where he is now almost insulin dependent, would mean that he has type 1B.

The understanding of the underlying pathology in type 1B is not yet understood. Some cases are linked to chromosomal changes, some may be a different form of an autoimmune response and some, in the light of a recent Japanese report, may reflect a transient islet cell destruction, perhaps by a virus. The important issue however is that about 50% can control blood sugars without insulin after a variable number of months and need only to rely on diet, exercise, and sometimes hypoglycemic drugs like Glucophage [metformin] to keep A1c levels within the normal range. Such evidence as there is, however, suggests there is still a degree of insulin insufficiency, and that in time insulin might again be needed. The type 1B category is quite rare in Caucasian families, about 5% of insulin dependent new onsets, but in African Americans and Hispanics, it comprises a little over 50%.

DOB