Endocrine Abstracts

Insulin autoimmune syndrome (Hirata syndrome) is a rare cause of hypoglycaemia. It was described by Hirata in 1970 and characterised as spontaneous hypoglycaemia, with elevated insulin levels, and associated high titres of insulin autoantibodies. It is most commonly reported in Japan and is associated with autoimmune disease or exposure to sulfhydryl-containing drugs.

Continuous glucose monitoring (CGM) devices measure interstitial glucose and were initially developed as an adjunct to blood glucose monitoring for use in individuals with diabetes mellitus. First generation devices provided short term, retrospective data, but newer devices allow real time monitoring with trend analysis and alerts predicting hypoglycaemia. NICE now recommends CGM for patients with type 1 diabetes with frequent or severe hypoglycaemia. Here we use this technology in the investigation and management of non-diabetes mellitus hypoglycaemia.

We present a case of a 76 year old, Caucasian gentleman, presenting with spontaneous hypoglycaemia in 2013. He gave a 12 month history of episodes of severe sweating associated with feeling vacant. Blood glucose was 1.5 mmol/l, insulin 2571.0 pmol/l (17.8–173) and C-peptide 652 pmol/l (298–2350). Subsequent imaging including an MRI of the pancreas, NM Octreotide scan with SPECT and NM whole body PET FDG did not reveal any evidence of an insulinoma. This gentleman was reassessed in 2016 following suspension of his driving licence and ongoing symptoms despite treatment with diazoxide. He underwent two 72 hour fasts that did not precipitate any spontaneous hypoglycaemia. A mixed meal test revealed blood glucose of 1.6 mmol/l at 300 minutes with insulin levels >6945 pmol/l. CGM showed large periods of time with hypoglycaemia. Insulin antibody IgG >200 mg/l (0–5).

His glycaemia continues to be difficult to control despite dietary advice and diazoxide. He finds the use of CGM invaluable as it predicts hypoglycaemia and allows prevention of episodes. As CGM is now real-time, more readily available, better tolerated and easy to use it may have an important role in the investigation and treatment of endocrine hypoglycaemia. To our knowledge this is the first use of this technology in the work up and management of non-diabetes mellitus hypoglycaemia.