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

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Abstract
OBJECTIVE To investigate the use of a calcium infusion test in the diagnosis and localisation of insulin secreting tumours in children. PATIENTS Three patients with persistent hypoglycaemia of infancy (PHHI). PROCEDURE 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. RESULTS 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. CONCLUSIONS 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. Calcium mediates insulin secretion at a cellular level In persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI) there is a defect in control of intracellular calcium in islet cells High external calcium levels increase intracellular calcium in islet cells from patients with PHHI Intra-arterial calcium gluconate injection stimulates insulin secretion from the pancreas in PHHI