A 37-year-old pancreas-kidney transplant recipient experienced severe, recurrent episodes of hypoglycaemia captured on a continuous glucose monitoring system (CGM). She had longstanding type 1 diabetes with multiple disease complications including end-stage nephropathy. She underwent a deceased donor simultaneous pancreas-kidney transplant after two years on haemodialysis. The transplanted pancreas was placed with systemic drainage into the common iliac vein.
Two months later she began experiencing neuroglycopenic symptoms 1-4 hours following meals. She progressed to have a witnessed generalized tonic-clonic seizure, presumably hypoglycemia induced. Biochemistry demonstrated a fasting hyperinsulinaemic state with blood glucose of 4.6mmol/L, C-peptide of 1.43nmol/L (0.3-1.30nmol/L), pro-insulin of 36pmol/L (<13.3) and insulin of 23.1mIU/L (0-17). A 48-hour fast failed to demonstrate significant hypoglycaemia, with the lowest recorded blood glucose of 3.5mmol/L. She demonstrated hyperinsulinaemia following completion of the fast with a post-prandial blood glucose of 9.6mmol/L, elevated C-peptide of 6.99nmol/L, and insulin of 162mIU/L.
A GCM was fitted and soon after she experienced another generalized tonic-clonic seizure. Severe fasting hypoglycaemia was captured during this episode, with capillary glucose readings of <2mmol/L lasting 70minutes. CGM traces also demonstrated frequent 1-4 hour post-prandial hypoglycaemic events. An extended glucose tolerance test with CGM monitoring confirmed ongoing hypersecretion of insulin with rises in insulin to 385mU/L at 90 minutes (normal <107mU/L) with glucose of 1.9mmol/L.
She was commenced on metformin, acarbose and a low-carbohydrate diet with self-reported and significant improvement in symptoms. The CGM system captured ongoing significant fasting and post-prandial hypoglycaemia despite symptom resolution.
Discussion:
Post-prandial hypoglycaemia following pancreatic transplantation is relatively common, however, it is usually mild and self-limiting. Potential aetiologies include peripheral hyperinsulinaemia, high titres of anti-insulin antibodies, increased insulin sensitivity, counter-regulatory hormone abnormalities and loss of allograft autonomic innervation. Diagnosis of this condition can be challenging and continuous glucose monitoring is a useful diagnostic tool when other measures fail to detect hypoglycaemic episodes.