Hypoglycemia Unawareness in IDDM
- Marian Mokan, MD,
- Asimina Mitrakou, MD,
- Thiemo Veneman, MD,
- Christopher Ryan, PHD,
- Mary Korytkowski, MD,
- Philip Cryer, MD and
- John Gerich, MD
- General Clinical Research Center, Washington University School of Medicine St. Louis, Missouri
- Departments of Medicine, Physiology, and Psychiatry, University of Pittsburgh School of Medicine Pittsburgh, Pennsylvania; the Second Department of Internal Medicine, Washington University School of Medicine St. Louis, Missouri
- Departments of Propaedeutic Athens University Athens, Greece; the Department of Biochemistry and Clinical Physiology, Washington University School of Medicine St. Louis, Missouri
- The Whittier Institute for Diabetes and Endocrinology La Jolla, California; and the Department of Medicine, Washington University School of Medicine St. Louis, Missouri
- Address correspondence and reprint requests to John E. Gerich, MD, University of Rochester Medical Center, 601 Elmwood Avenue Box CRC, Rochester, NY 14642.
Abstract
OBJECTIVE To assess the characteristics of patients with hypoglycemia unawareness (development of neuroglycopenia without appropriate prior autonomic warning symptoms) and its predisposing factors.
RESEARCH DESIGN AND METHODS We studied 43 insulin-dependent diabetes mellitus patients who were objectively categorized as having or not having hypoglycemia using the stepped hypoglycemic clamp technique in which plasma glucose was clamped at plateaus of 4.3, 3.6, 3.0, and 2.3 mmol/l and a statistical criterion (onset of autonomic warning symptoms at a plasma glucose concentration 2 SD below normal) and examined their clinical characteristics and hormonal, symptomatic, and cognitive responses.
RESULTS Eleven (26%) of the patients were classified as having hypoglycemia unawareness. Compared with the other patients, unaware patients had a lower HbA1c level (P < 0.01), a longer duration of diabetes (P < 0.01), and a history of more severe hypoglycemia (P < 0.003). During experimental hypoglycemia, counterregulatory hormone responses, neuroglycopenic symptoms, and cognitive dysfunction all began at lower plasma glucose concentrations in unaware patients (P < 0.01, 0.03, and 0.01, respectively). Moreover, although the magnitudes of their plasma catecholamine responses and autonomic symptoms were reduced (both, P < 0.01), the plasma catecholamine levels at which autonomic symptoms began was not altered. Finally, as seen from glucose infusion rates necessary to maintain identical plasma glucose levels, patients with hypoglycemia unawareness had increased sensitivity to insulin (P < 0.001).
CONCLUSIONS Our results confirm an association between hypoglycemia unawareness and duration of diabetes, glycemic control, and occurrence of severe hypoglycemia, and in addition provide evidence that both autonomic and neuroglycopenic symptoms are affected and that insulin sensitivity is increased, but β-adrenergic sensitivity is not diminished.
- Received August 16, 1993.
- Revision received February 17, 1994.
- Accepted February 17, 1994.
- Copyright © 1994 by the American Diabetes Association
