Avoiding Low Blood Sugar Levels Restores Diabetic Patients' Ability To Recognize the Warning Symptoms of Low Blood Sugar

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The summary below is from the full report titled "Avoidance of Hypoglycemia Restores Hypoglycemia Awareness by Increasing ß-Adrenergic Sensitivity in Type 1 Diabetes." It is in the 1 May 2001 issue of Annals of Internal Medicine (volume 134, pages 729-736). The authors are A Fritsche, N Stefan, H Häring, J Gerich, and M Stumvoll.

What is the problem and what is known about it so far?

Diabetes is a disease characterized by elevations in blood sugar (glucose). Insulin treatment reduces glucose levels, sometimes below normal levels. Extremely low levels of glucose can cause changes in mental function, seizures, and coma. Diabetic patients can usually sense early warning symptoms of low blood sugar, such as sweating, hunger, tremor, or fast heart rate. These warning signs probably depend on the release of adrenalin-like hormones. Unfortunately, some patients stop developing these warning signs, particularly after many episodes of low blood sugar. These people are more likely to have very low levels of glucose, which sometimes result in serious injury.

Why did the researchers do this particular study?

To see whether strict avoidance of low sugar levels restores warning symptoms in diabetic persons and whether adrenalin-like hormones and sensitivity to these hormones play a part in these warning symptoms.

Who was studied?

The study included 10 men receiving insulin for childhood onset–type diabetes. All had had extremely low blood sugar levels that resulted in seizures, coma, or the need to receive glucose through a vein, as well as frequent low blood sugar levels without warning symptoms.

How was the study done?

The men were instructed to measure blood sugar levels five times daily. On the basis of these measurements, insulin dosages were modified to keep sugar levels above a safe level of 70 mg/dL (milligrams per deciliter). Over 4 months, insulin dosages were decreased by an average of about 25%. At the end of this time, the researchers injected enough insulin through a vein to induce low sugar levels and observed whether the men now had warning symptoms. They also tested the men's sensitivity to an adrenalin-like hormone injected into a vein.

What did the researchers find?

None of the men had extremely low blood sugars or severe symptoms during 4 months of daily insulin treatment. The occurrence of blood glucose levels less than 70 mg/dL decreased from an average of 8 times per week to once per week, and average levels of blood sugar increased. When low sugar levels were produced in the research unit, the men experienced warning symptoms. They also responded more strongly to injections of adrenalin-like hormone after 4 months without low blood sugar levels than they did before.

What were the limitations of the study?

The study was small, included only men, and was conducted under carefully controlled circumstances rather than in "real-life" conditions. Long-term harms of altering glucose control were not studied.

What are the implications of the study?

Diabetic patients who are treated with insulin and who have recurrent episodes of low blood sugar may lose their ability to detect low glucose levels, probably because they lose sensitivity to adrenalin-like hormones. The ability to detect low glucose levels may be restored after even a short period of strict avoidance of low glucose levels.