Endocrine Abstracts

Introduction: Insulinoma is rare tumor with an incidence of 1 in 250,000 patient-years. It presents with repeated episodes of hypoglycemia due to endogenous hyperinsulinemia, which occurs mostly in the fasting state. Insulinomas are usually sporadic, solitary, benign and encapsulated small lesions and majority of them measure <2 cm in diameter. They pose a challenge for pre-operative localization.

Materials and methods: A retrospective study of patients diagnosed with insulinoma during the period 1999–2018 (19 years) was done. Biochemical diagnostic criteria used were plasma concentrations of glucose <0.5 g/L with corresponding insulin level >3.0 μU/ml and C-peptide of >0.6 ng/ml. The localization of the tumor was done by various modalities namely computed tomography (CT), magnetic resonance imaging (MRI) and intra-operative ultrasonography (IOUS).

Results: Seven cases of insulinoma were included in the analysis, aged between 26 and 80 years, with a median age of 50.7 years. There were 3 males and four females (sex ratio 75%). All of them presented adrenergic features (sweating, shakiness, tachycardia, anxiety, and a sensation of hunger) and only one presented neuroglycopenic signes. Eighty-five percent of patients presented with pre-prandial hypoglycemia. There was weight gain in 57%. Hypoglycemia was spontaneous in 4 cases and 72-hour fasting plasma glucose test was necessary in other 3 cases. The average Plasma concentration of glucose was 0.42 g/l with corresponding insulin level 18.33.0 μU/ml(4.2–380 μU/ml) and C-peptide of 4.63 ng/ml (1.6–9.55 ng/ml). Different modalities were employed for pre-operative localization of these patients out of which 1 (14.2%) cases were localized with CT, 2 (28.5%) cases with MRI and 4 (57%) of them could not be localized out of which 2 were localized by IOUS. Among 7 cases, 4 underwent surgery out of which one patient underwent distal pancreatectomy as tumor was not localized and 3 underwent enucleation. In all the cases, the size of the insulinoma ranged between 1 and 2 cm. All patients were cured after surgery with no complications except 1 patient presented a transient pancreatitis.

Conclusion: In a non-diabetic patient with hypoglycemia, the diagnosis of insulinoma should be kept in mind. The commonest presentation in our series was pre-prandial hypoglycemia. A proper diagnosis and management can have a great impact on outcome and survival so it is important to address this.