B

Glucagon raises blood glucose by mobilizing hepatic glycogen. It therefore works best when liver glycogen stores are plentiful, as in infants who are large-for-dates or born to diabetic mothers and in hyperinsulinemic states such as nesidioblastosis. In classic galactosemia the primary hepatic enzyme block (galactose-1-phosphate uridyl transferase deficiency) quickly depletes glycogen and impairs gluconeogenesis, so a glucagon bolus produces little or no rise in glucose, making it ineffective for persistent hypoglycaemia in this disorder [Stanley, 1997, PMID 9130925; Sprangers, 2001, PMID 11277381].