Endocrine Abstracts

Background: Patients with an insulinoma are at variable risk of severe hypoglycemia due to wide ranges of both tumoral insulin secretion and peripheral tissue sensitivity to chronic hyperinsulinaemia.

Objectives: In this study we investigated the clinical, biological and tumoral characteristics of a large series of patients with immunohistochemically confirmed insulinoma and we assessed both insulin sensitivity and beta-cell function in fasting steady-state conditions.

Methods: This was a retrospective analysis of 48 patients with an insulinoma, in whom insulin sensitivity and beta-cell function were evaluated by a fasting HOMA test.

Results: The median age at the time of diagnosis was 51 years (range: 17–83) and mean BMI was 26.6±10.6 kg/m². In 8 patients (17%), the diagnosis of malignant insulinoma was considered. Pre-operative localization was possible in 94% of the patients. The most sensitive imaging methods were echo-endoscopy (sensitivity 92%) and intra-operative ultrasonography (sensitivity 97%). The average diameter of the tumors was 20.3 mm and the most frequent localizations were the head (28%) and body (57%) of the pancreas. Successful post-surgical remission was finally obtained in 80% of the cases.

The fasting glucose level was variable, ranging from 25 to 116 mg/dl. Insulin sensitivity (assessed by HOMA-S) ranged from 9.7% to 336% (median value 75%) and beta-cell function (assessed by HOMA-B) varied from 47% to 2544% (median value 563%). No difference of insulin sensitivity was observed as a function of gender or age. A significant negative correlation (r=−0.30, P<0.05) was observed between insulin sensitivity and body mass index (BMI) and a negative correlation (r=−0.18, P<0.05) was found between insulin sensitivity and tumor size in women but not in men.

Conclusions`: Patients with an insulinoma usually show slightly decreased but very variable insulin sensitivity which may help to explain their differential susceptibility to undergo severe hypoglycemia.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.