Endocrine Abstracts

Factitious hypoglycaemia is characterised by high insulin levels but accompanied with low Proinsulin and C-peptide levels and a negative sulfonylurea screen

We present a 54-year-old woman who was initially diagnosed with type 2 diabetes in 2002 and by 2004, she was converted to insulin treatment due to poor tolerance to Metformin. She also had a previous history of Manic depressive psychosis and treated with lithium.

In the months prior to her admission, due to persistent hypoglycaemic episodes, her insulin requirement had to be dramatically reduced from a total of 60 to 15 units/day.

She was admitted with repeated, severe episodes of neuroglycopenia, and after stopping all forms of insulin, was monitored as an in-patient. Her 4-hourly blood glucose level remained between 3 and 7 mmol/l and was interspersed with further hypoglycaemic episodes. During one such episode, her blood glucose was as low as 1.4 mmol/l but her concomitant plasma insulin levels was <2 pmol/l (Perkin Elmer insulin immunoassay; normal=0–60 pmol/l) and C-peptide was 46 pmol/l (174–960 pmol/l). Urinary screen for sulfonylurea was negative. Insulinoma investigated with a dynamic CT scan of the pancreas and IFG-2:IGF-1 ratio 2.2 (normal: <10). She bafflingly continued to have dramatic and sustained hypoglycaemia despite not receiving any insulin. At a subsequent hypoglycaemic episode with blood glucose of 1.2 mmol/l, standard methods did not detect any insulin but an alternative assay method (Delfia insulin assay) showed insulin Aspart levels of >200 pmol/l.

Subsequent follow up revealed that she had been working at the same mental care home, where-in she previously was a patient. Her hypoglycaemic symptoms have now ceased and she is doing well on Metformin alone. At this modern age of insulin analogues, this fascinating story reminds us the need of awareness about the complexities of insulin assays, and their importance in diagnosing factitious hypoglycaemia.