Intra-arterial calcium stimulation test in the investigation of hyperinsulinaemic hypoglycaemia

To investigate the use of a calcium infusion test in the diagnosis and localisation of insulin secreting tumours in children.

Three patients with persistent hypoglycaemia of infancy (PHHI).

During planned selective coeliac and mesenteric arteriography, serial samples were taken from a catheter in the right hepatic vein for insulin measurement following the injection of calcium gluconate.

In all three children, selective intra-arterial calcium stimulation produced a significant rise in plasma insulin and was of value in localising the pancreatic abnormality in one child. In vitro studies on islets of Langerhans isolated from this patient following partial pancreatectomy showed unresponsive intracellular calcium signalling of the cells when stimulated with high extracellular concentrations of glucose and potassium or with sulphonylurea drugs (tolbutamide), but normal responsiveness to increasing extracellular calcium concentrations.

The findings suggest a functional abnormality of the calcium channel in PHHI and provide a rationale for the reported efficacy of channel blocking drugs in this condition. The role of selective intra-arterial calcium stimulation in the diagnosis of hyperinsulinaemic hypoglycaemia in childhood warrants further investigation.