Objective: Reactive hypoglycemia is a common medical problem whose pathophysiology is not completely understood. The objective of this study was to investigate the prevalence of autonomic nervous system abnormalities in patients with reactive hypoglycemia compared with controls.
Methods: Six women, mean age 31 +/- 5 years, with reactive hypoglycemia, and 5 healthy controls women aged 24 +/- 4 years were studied. We investigated the heart rate variability and blood pressure changes after an upright tilt with and without an isoproterenol infusion. A positive result was defined as syncope or presyncope associated with bradycardia, hypotension or both.
Results: In response to the orthostatic stress alone or in conjunction with a 4 micrograms isoproterenol infusion, 5 of 6 patients had a positive test as did one of the five control subjects. Patients had a baseline hyperadrenergic tone, with a sympathetic to parasympathetic ratio of 2.3 +/- 0.8 under basal conditions and 10.1 +/- 4.1 during the isoproterenol infusion, compared to 0.7 +/- 0.3 (p = 0.06) and 0.5 +/- 0.1 (p < 0.01) respectively, in the control group.
Conclusion: Patients with reactive hypoglycemia may be at the extreme end of a spectrum of normal biologic variability, they may have an hyperadrenergic tone and, after a provocative stimulus, sympathetic nerve firing and or synaptic release of NE may not be sufficient to maintain an adequate vascular tone. Alternatively, the vascular response to NE may be impaired. An excessive and paradoxic vasovagal or parasympathetic response was not observed.