Recent studies suggest that insulin-dependent diabetes mellitus patients switched from animal to human insulin may have decreased awareness of hypoglycemic warning symptoms. The risk of severe or fatal hypoglycemia associated with the treatment of diabetes increases with age. We conducted these studies to determine if awareness of hypoglycemic warning symptoms was greater with animal than with human insulin in elderly patients with diabetes. Nonobese elderly patients with non-insulin-dependent diabetes mellitus (NIDDM) (n = 13; age, 74 ± 1 years; body mass index, 26.6 ± 0.7 kg/m2) underwent paired hyperinsulinemic glucose clamp studies (insulin infusion rate 60 mU ç m−2 ç min) in random order. In one study, regular human insulin was infused, and in the other study, regular beef/pork insulin was infused. In all studies, plasma glucose was decreased from fasting levels to 5 mmol/l during the first 60 min and was then allowed to fall to 4.4, 3.8, 3.3, and 2.8 mmol/l in each subsequent hour. Subjects were blinded as to which study they were undergoing. In each study, a hypoglycemic symptom checklist was administered, and counterregulatory hormones were measured every 15 min. Neuropsychological tests were performed every hour. Counterregulatory hormone responses to the two insulin preparations were similar. Autonomic (P < 0.05) and neuroglycopenic (P < 0.01) symptom scores were significantly higher during the beef/pork insulin studies. The responses on the neuropsychological tests were not significantly different. We conclude that beef/pork insulin results in greater awareness of hypoglycemic warning symptoms than does human insulin in elderly patients with NIDDM.

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