Deciphering the Enigma of Postprandial Hyperinsulinaemic Hypoglycaemia After Bariatric Surgery, Part 1 A: Assessing Insulin Turnover Using an In-vivo Deuterated Water Experiment. A Proof-of-concept Study.

Despite an increased prevalence, the underlying pathophysiology of PHH remains incompletely understood. It is generally assumed that PHH is caused by excess insulin secretion, either due to an intrinsic beta-cell abnormality (histology showing increased beta-cell mass or signs of hyperfunction) and/or increased postprandial insulinotropic signals (also known as the incretin-effect) as a consequence of the re-arranged gastrointestinal tract and accelerated nutrient transit and absorption. Either of the two explanations would imply an altered insulin turnover in these patients with higher amounts of pre-stored insulin and/or accelerated de-novo insulin synthesis in response to stimulus-depletion of the available insulin pool. A non-invasive in vivo technique to study insulin turnover has not been established yet and data related to PHH are consequently lacking.

The primary objective of this study is to observe the kinetics of pre-stored and de-novo synthesized insulin that is secreted into the circulation using an in-vivo heavy water (D2O) labelling experiment in patients with postprandial hyperinsulinaemic hypoglycaemia (PHH) and non-surgical non-PHH controls. The investigators hypothesize that the suggested methodological approach is feasible to assess insulin turnover and provides the foundation for further studies in different target groups.