Anti-insulin antibodies may cause hypoglycaemia following pancreas transplantation

Abstract

Some pancreas transplantation (PTX) recipients experience hypoglycaemia after transplant. We studied the incidence and pattern of hypoglycaemic symptoms following PTX and later studied the glucose and pancreatic hormone response to Sustacal in patients with and without hypoglycaemia following PTX. In a survey of 54 PTX recipients who were 2 to 33 months post-transplant, 29 reported symptoms of hypoglycaemia at any time following their transplant. Of 12 patients who tried to document their blood glucose during any episode, 5 had a blood glucose less than 3.3 mmol/l, and another 5 documented a blood glucose from between 3.33 and 3.88 mmol/l. The patients reporting symptoms were less likely to be insulin resistant with longer time post-PTX, lower body mass index (BMI), and on lower doses of prednisone. Later, 12 patients with established, repeated episodes of hypoglycaemia following PTX were case-matched to PTX recipients without hypoglycaemic symptoms. Fasting glucose, free and total immunoreactive insulin (IRI), C-peptide, proinsulin and glucagon were measured following a 4 h Sustacal challenge. The hypoglycaemic group was further divided into those whose glucose rose after Sustacal (Hypo-High) and those whose blood glucose did not rise from baseline concentration (Hypo-Flat). The Hypo-High subgroup had a lower fasting free/total IRI ratio in addition to a greater increase in blood glucose after Sustacal compared with either Hypo-Flat or non-hypoglycaemic transplant recipients. The low free/total insulin ratio and hyperglycaemic response to Sustacal are consistent with the presence of anti-insulin antibodies, an established cause of hypoglycaemia. In summary, documented hypoglycaemia, while uncommon, may occur and be significant following PTX. Anti-insulin antibodies may be one of the many factors contributing to hypoglycaemia in this population.