Endocrine Abstracts

Background: Adult spontaneous hypoglycaemia in non-diabetic patients is not a diagnosis per se but a manifestation of a disease and is often a diagnostic challenge. Although rare, it’s important to exclude endogenous hyperinsulinemia, because treatment can be curative. The aim of our audit was to assess the usefulness of various investigations done for spontaneous hypoglycaemia in diagnosing Insulinoma.

Methods: Data on 98 non-diabetic patients referred to our endocrine unit for investigation of hypoglycaemia was obtained. Data was gathered for type of biochemical investigations undertaken – 24 /72 h fast, prolonged glucose tolerance test/mixed meal test (pGTT), insulin/C-peptide levels, radiology investigations, endoscopic ultrasound, and the diagnostic outcomes.

Results: Of n=98, their age 44.5±14.1 (mean±S.D.) years, Females 62%. Prolonged GTT was undertaken in 72 (73%), 24-h fast in 77 (78%) and 72-h fast in three patients. 51 patients (52%) had both 24-h fast and GTT. Prolonged GTT: 27 (27%) had hypoglycaemia on the prolonged GTT. 21/27 had 24 h fast (none had hypoglycaemia on 24 h fast). One had 72 h fast (normal). Insulin/C-peptide abnormal in two patients (one had insulinoma and one had normal pancreas on further investigations). Pancreatic imaging: CT, MRI, and EUS undertaken in 13, 2, and 8 patients respectively. Final diagnosis was Reactive hypoglycaemia in 22 (81.5%) and diabetes mellitus/IGT in four patients and insulinoma in one. 24 h fasting: 6 (7%) patients had hypoglycaemia on 24 h fasting. Five had abnormal insulin/C-peptide with the hypoglycaemia. CT/MRI and EUS imaging was undertaken in all these six patients. Insulinoma proven in four patients, one factitious hypoglycaemia, and one NIPHS.

Conclusion: Prolonged GTT did not add to the 24 h fasting test in the diagnosis of insulinoma, though it picked up other diagnoses.