Genetic hypoglycaemia in infancy and childhood: pathophysiology and diagnosis.

Abstract

Glucose, like oxygen, is of essential and fundamental importance for brain metabo- lism. The major source of brain glucose is the blood supply and thus a severe encephalopathy will ensue when the glucose content of blood becomes de—cient. A prompt diagnosis is essential and must be achieved safely with an appropriate test. This requires knowledge of the homeostatic mechanisms that maintain the blood glucose concentration between the relatively narrow range of 2.5 and 7.5 mmol/L whether the child is eating or fasting. Within the last decade, many new insights and facts have expanded our knowledge considerably in elucidating the causes and mechanisms of genetic hypoglycaemias. This brief review outlines certain aspects of the regulation of glucose homeostasis and focuses on the causes of genetic hypogly- caemias, in which signi—cant advances have been made recently. DEFINITION After the —rst 72 h of life (term babies) or the —rst week (pre-term babies), hypogly- caemia is generally de—ned as a plasma or capillary whole-blood glucose concentra- tion less than 2.5 mmol/L (Walker 1994). Although it is highly controversial (Cornblath et al 1990; Volpe 1995), there is a growing consensus that in neonates levels above 2.5 mmol/L are desirable. Moreover, and most importantly, these lower limits are probably exceeded when concomitant insults that increase cerebral demand for glucose (like hypoxaemia and ischaemia) accompany hypoglycaemia.