Endocrine Abstracts

Introduction: Hypoglycemia is the most frequent metabolic complication observed in patients with type 2 diabetes mellitus (T2DM). Moreover, rare insulinomas are the most common cause of endogenous hyperinsulinemic hypoglycemia in adults. The coincidence of insulinoma in a patient with pre-existing T2DM is an extremely rare condition and there are few case reports in the medical literature.

Case report: A 76-year-old woman diagnosed with T2DM 6 years ago, was referred to our hospital because of recurrent episodes of hypoglycemia. Her diabetes was treated with metformin, 1750 mg/day having a good metabolic control (HbA1c: 5.7%). About 4 years after she was diagnosed with T2DM, she had experienced an initial episode of hypoglycemia. The dose of oral anti-diabetics was reduced. However, although drug dose was lowered hypoglycemic events began to be recurrent. Even though the therapy was discontinued at the end, persistent episodes were still occurring. Complete physical examination was normal. Her laboratory profile showed normal renal and liver functions. Also, thyroid and adrenal dysfunctions were excluded. Laboratory profile from a prolonged fasting test showed inappropriately elevated plasma insulin and C-peptide levels in presence of hypoglycemia (plasma glucose, 36 mg/dl; insulin, 67.1 mU/ml; and C-peptide, 8.97 ng/ml). A CT-scan revealed a 2.2 cm sized mass in the pancreatic tail. The patient underwent surgery and hystopathological diagnosis revealed insulinoma. One year after resection, C-peptide levels and plasma insulin are in normal range and hyperglycemia due to T2DM persists. She is currently being managed with gliclazide 90 mg/day without any further hypoglycemic events.

Conclusions: If hypoglycemia persists despite stopping diabetes treatment, other causes should be considered. Although this is an infrequent condition, clinicians should bear in mind that insulinomas may exist together with T2DM, and it is important to have this suspicion for the prevention of morbidities.