Octreotide exacerbated fasting hypoglycaemia in a patient with a proinsulinoma; the glucostatic importance of pancreatic glucagon.

Octreotide, a long-acting somatostatin analogue, has been used to alleviate hypoglycaemia in patients with insulinomas. Transient worsening of fasting hypoglycaemia following octreotide has also been described (Stehouwer et al., 1989). We describe a patient with a 'proinsulinoma' in whom octreotide caused rapid and prolonged symptomatic worsening of fasting hypoglycaemia. Catecholamine and cortisol counterregulatory hormonal responses were normal but those of glucagon and GH were impaired. Acute neuroglycopaenic symptoms were present during octreotide induced hypoglycaemia, which was accompanied by and attributed to an acute reduction in pancreatic glucagon secretion in the presence of persistent and unsuppressed hyperproinsulinaemia. This suggests that glucagon may be important in maintaining glucose homeostasis in chronic hypoglycaemia due to endogenous hyperinsulinism even though its concentration in the peripheral blood is not raised.