Hypoglycemia

Hypoglycemia is characterized by 1) central nervous system (CNS) symptoms, including confusion, aberrant behavior, or coma; 2) a simultaneous blood glucose level ≤50 mg/dl; and 3) symptoms being resolved within minutes following glucose administration (Fig. 1).

Hypoglycemia is a medical emergency because the CNS has an absolute requirement for a continuous supply of bloodborne glucose to serve as a metabolic fuel. Transient hypoglycemia can cause cerebral dysfunction, whereas severe, prolonged hypoglycemia causes brain damage. Therefore, it is not surprising that the body has multiple overlapping mechanisms to prevent or correct hypoglycemia. The most important hormone changes in combating hypoglycemia are increased secretion of glucagon and the catecholamines, combined with decreased insulin secretion.

Figure 1: A. Actions of some of the glucoregulatory hormones in response to low blood glucose. B. Glycemic thresholds for the various responses to hypoglycemia. [Note: Normal fasted blood glucose is 70−99 mg/dl.] + = weak stimulation; ++ = moderate stimulation; +++ = strong stimulation; 0 = no effect; ACTH = adrenocorticotropic hormone.