Endocrine Abstracts (2018) 55 CB14 | DOI: 10.1530/endoabs.55.CB14

Insulinoma - a cause of recurrent hypoglycaemias

Annalisa Montebello & Sandro Vella

Mater Dei Hospital, Msida, Malta.

A 72 year old lady presented to endocrine clinic in January 2016 with a history of frequent episodes of feeling increasingly lightheaded, tremulous, sweaty and hungry. All symptoms resolved after eating. Her family doctor had twice documented a capillary glucose lower than 4 mmol/l. Continuous blood glucose monitoring was performed but there were no episodes of hypoglycaemia picked up. She was admitted for a 72 h fast in September 2016. Her capillary blood glucose readings never dropped to below 2 mmol/l during the test. At the end of the fast, a plasma glucose, insulin, C peptide, pro insulin, beta hydroxybutyric acid levels and urine for sulphonylurea were taken revealing:

Fasting Glucose: 2 mmol/l (3.88–6.38 mmol/l)

Insulin: 7.8 μU/ml (2.6–25 μU/ml)

C peptide: 1.5 ng/ml (1.1–4.4 ng/ml)

Pro Insulin: 12.1 pmol/l (<11 pmol/l)

Beta hydroxybutyric acid: 1687 μmol/l (Up to 270 μmol/l)

Urine for sulphonylurea: negative

These results were diagnostic of an insulinoma. Magnetic rsonance (MR) imaging of the pancreas in December 2016 failed to show any pancreatic lesions. An endoscopic ultrasound (US) of the pancreas was performed showing a 13× 6 mm hypoechoic homogenous lesion at the body of the pancreas. Pancreatic core biopsies confirmed a Grade 1 (low grade) neuroendocrine tumour. A repeat MR pancreas in May 2017 showed a 9mm focus of restricted diffusion at the junction of the body and tail of the pancreas which probably corresponding to the neuroendocrine tumour seen on endoscopic US. Subcutaneous Octreotide was prescribed to prevent hypoglycaemia. The patient underwent successful distal pancreatectomy in July 2017. Localisation of tumour was guided by on table intra-operative US. She was noted to have high capillary blood glucose readings post operatively and an oral glucose tollerance test confirmed a diagnosis of diabetes mellitus (fasting blood glucose of 10.44 mmol/l, second hour 21.9 mmol/l. She is currently managed on oral glucose lowering agents and is doing well. Insulinomas are the commonest neuroendocrine tumours. They arise from pancreatic islet cells and may secrete insulin in short bursts thus causing rapid fluctuation in blood glucose levels. 90% are benign tumours. 5% are malignant. Diabetes mellitus is one of the main complications post operatively.

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