Endocrine Abstracts

Introduction: In 2009 the Endocrine Society’s clinical practice guidelines for management of hypoglycemic disorders, confirming previous suggestions, have stated that the new cut-off of insulin for the diagnosis of insulinoma should be lowed to 3 μU/mL in presence of hypoglycemia (serum glucose ≤55 mg/dL). Moreover hypoglycemia in post-prandial status has been reported in insulinoma, alone or associated with fasting hypoglycemia. Finally preexisting diabetes mellitus is increasingly recognized in these patients.

Aim: To evaluate clinical features and diagnostic criteria in a monocentric series of insulinomas including sporadic and multiple endocrine neoplasia type 1 (MEN-1) patients. In addition anamnestic glucose metabolic profile was investigated.

Patients and methods:: Clinical and biochemical data regarding 33 patients including 27 sporadic and 6 MEN1 were retrospectively analyzed.

Results: The 72 hour fasting test was positive in all cases. However in one case it was initially negative since hypoglycemia did not occur, but became positive after 2 year follow-up. Three patients showed a nadir insulin level >3 μU/ml but <6 μU/ml. In the remaining 30 cases lowest insulin level was >6 μU/ml. At presentation 27 patients (82%) reported only fasting symptoms, 3 (9%) only post-prandial symptoms and 3 (9%) both. Four cases (12%) had been previously affected by type 2 diabetes mellitus and 4 cases by impaired fasting glucose

Conclusion: The new cut-off of insulin has further increased the sensitivity of 72 h fasting test for the diagnosis of insulinoma from 87 to 100% in patients. However the absence of hypoglycemia during test does not rule out in definitive manner the diagnosis and the test should be repeated in any high suspicion case. Surprisingly previous glucose metabolism alterations are not infrequent and require further evaluation in wider series.

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.