Hypoglycaemia

• Hypoglycaemia is defined as ‘A plasma glucose concentration low enough to cause symptoms and/or signs of impaired brain function’. • Cut-offs are contentious, ranging from <2.2 to <4.0 mmol/L, and are dependent on age, diagnosis, and also availability/usage of alternative metabolic fuels such as ketones. • May be transient or persistent, dependent on diagnosis. • Causes broadly due to: ◦ decreased glucose including prematurity, inborn errors of metabolism, hypopituitarism, adrenal insufficiency (primary and secondary), and prolonged fasting ◦ increased glucose utilization including infant of diabetic mother, hyperinsulinaemia, perinatal asphyxia, and various syndromes, e.g. Beckwith–Wiedemann. • Endocrine causes of hypoglycaemia include growth hormone deficiency, adrenal insufficiency (primary and secondary), and (?) hypothyroidism. • Metabolic disorders cause hypoglycaemia via impaired: ◦ mobilization of glucose stores ◦ gluconeogenesis ◦ alternative energy sources ◦ liver function. • Hyperinsulinaemic hypoglycaemia presents with increased glucose requirements (>8 mg/kg/minute) and non-ketotic hypoglycaemia. Diagnosis confirmed by demonstrating raised/detectable insulin/C-peptide during hypoglycaemia. Genotyping may assist with not only diagnosis but direct therapy (medical and surgical).