Blood Glucose in Suspected Hypoglycemia

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Abstract
Palardy et al. (Nov. 23 issue)1 did not find a significant correlation between symptoms of hypoglycemia and levels of blood glucose in patients with suspected postprandial hypoglycemia. However, symptoms of hypoglycemia (such as weakness, palpitations, tremor, sweating, and headache), as the authors correctly point out, are characteristic of stimulation of the sympathetic nervous system. Therefore, the question arises whether these patients had greater than normal stimulation of the sympathetic nervous system in the absence of marked hypoglycemia (as the clinical counterpart of the absence of symptoms in patients with autonomic failure, in whom hypoglycemia develops). Unfortunately, no data were presented on plasma levels of norepinephrine, as a marker of sympathetic nervous stimulation. Meals rich in carbohydrates and oral glucose loading may impose a serious load on blood-pressure homeostasis.2 , 3 In elderly subjects and in young patients with hypertension (in the same age range as those studied by Palardy et al.) this can result in a decrease in blood pressure.3 This phenomenon is specific to glucose, since oral protein and fat loading has no effect on blood pressure.4 In addition, the symptoms of postprandial hypoglycemia seem characteristically to improve when the patient follows a diet with high levels of protein and the restriction of carbohydrates.5 Therefore, we propose that the symptoms suggestive of postprandial hypoglycemia in the relatively young patients in the study of Palardy et al. are primarily the result of the strong adrenergic reflexes evoked by the effects of oral carbohydrates on the circulation.