Endocrine Abstracts

Case History: A 69-year-old gentleman was admitted having lost consciousness. This episode was preceded by typical hypoglycaemic symptoms which, in retrospect, he had experienced for four decades with increasing frequency and severity over the past year. He was hypertensive. There was no family history of endocrinopathy or diabetes.

Investigations: A supervised inpatient fast was undertaken along with cross-sectional and radio-isotope imaging.

Results and Treatment: Hypoglycaemia (glucose 1.8 mmol/l) occurred following an overnight fast. Corresponding insulin and c-peptide measurements were inappropriately detectable – consistent with endogenous hyperinsulinaemic hypoglycaemia. Serum calcium and cortisol were normal.

Abdominal imaging revealed a large locally invasive left supra-renal mass with associated lymphadenopathy which was both FDG- and MIBG-avid. There was also diffuse mild FDG uptake throughout the pancreas without an anatomical correlate.

These unexpected imaging findings prompted further investigations. Chromogranin A and B and urine normetadrenaline were all elevated – consistent with a tumour of neuroendocrine origin.

We postulated that this tumour might be releasing a secretagogue that was stimulating pancreatic insulin release. Analysis of incretin hormones at the time of hypoglycaemia revealed a markedly and inappropriately elevated GLP-1 in combination with an undetectable neurotensin (co-secreted with GLP-1 from the gut). This is suggestive that the observed hyperinsulinaemia was mediated by tumoural GLP-1 production.

Hypoglycaemia was eliminated by somatostatin analogue therapy. Whilst awaiting surgery he represented with weight loss and worsening abdominal pain. Repeat imaging showed disease progression such that surgery was no longer felt to be in his best interests. He underwent chemotherapy with stable disease after four cycles.

Conclusions and points for discussion: We describe a unique case of symptomatic hyperinsulinaemic hypoglycaemia mediated by tumoural GLP-1 release from a malignant MIBG and FDG-avid adrenal lesion.