Endocrine Abstracts

A 52 year old lady with hypothyroidism and hypertension was referred by her GP for unexplained low blood glucose on several occasions. There was history of vacant spells with confusion and disorientation over the previous year. When referred for neurological assessment, no abnormality was identified. Her medications included amlodipine 5 mg, ramipril 10 mg, thyroxine 50 mcg, loratidine 10 mg. Her BMI was 44 kg/m².

Additional investigations arranged by GP included, cortisol (0920 h) 184 nmol/l, short synacthen test (0 min) 331 nmol/l and (30 min) 602 nmol/l, eGFR 62 ml/min.

She reported significant weight gain over the last few years, compared with her twin sister who had a normal BMI. She drinks Lucozade when feeling ‘under the weather’.

A prolonged OGTT was performed as an outpatient. She did not complain of any symptoms of hypoglycaemia, no insulin/C-peptide samples were taken.

Analysis of the plasma glucose samples showed hypoglycaemia occurring at 3 h (1.6 mmol/l), rising slowly to 2.3 mmol/l at 4½ h.

An admission was arranged for further assessment. Initially her FBG was 3.6 mmol/l, insulin 197 pmol/l, C-peptide 443 pmol/l. After breakfast she developed postprandial hypoglycaemia (plasma glucose 2.0 mmol/l with a further increase in insulin and C-peptide levels: 682 and 1537 pmol/l respectively. A sulphonylurea screen was negative.

CT scan showed 14 mm hypervascular tumour within tail of pancreas consistent with insulinoma. Cytology from an FNA showed features in keeping with a well differentiated neuroendocrine tumour.

She underwent distal pancreatectomy and splenectomy in June 2011. She was reviewed subsequently in clinic, asymptomatic and successfully losing weight.

Insulinoma presenting as post-prandial hypoglycaemia only is an uncommon presentation of a rare tumour. These patients often have hypoglycaemia unawareness, so close clinical evaluation and monitoring of capillary glucose is vital to avoid unnecessary delays in diagnosis.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.