Endocrine Abstracts

Background: Identifying the etiology of hypoglycemia in a non-diabetic patient is a significant challenge. Hyperinsulinemic hypoglycemia can lead to pancreatectomy in patients with no evident organic disease. Insulin autoimmune syndrome (IAS) or Hirata diseaseand Type B insulin resistance syndrome are the two typesof autoimmune hypoglycemia, with a low worldwide prevalence.

Objective: We report two real-lifecases that illustrate each of them.

Results: The first case depicts a 69-year-old woman who had frequent episodes of symptomatic hypoglycemia, which happened to occur three hours after the intake of food. Amonth earlier, she had received a 7-day treatment with amoxicillin. Besides, she had a daughter with type 1 diabetes, celiac disease and autoimmune subclinical hypothyroidism. She underwent a prolonged fast test in which no clinical or analytical hypoglycemia were found. Nevertheless, severe hyperinsulinemia was detected, even though it wasnot correlated with the levels of serum glucose, C peptide and proinsulin, which showed normal values. Insulin autoantibodies (IAA) were positive with a 76.8% fixation (RV < 8.2%). Moreover, there was no pathological finding within HbA1, nor the adrenal, thyroid and somatotroph axis. In addition, sulfonylureas were not detected in urine. Afterwards, the oral glucose tolerance test showed initial hyperglycemia (insulin bound by IAA becomes ineffective), followed by hypoglycemia due to the release of the insulin-IAA complexes. A diet low in simple carbohydrates and frequent intake of small meals encouraged a successful clinical evolution of the IAS. On the other hand, the second patient was a three-year-old girl, with neonatal diagnosis of DiGeorge syndrome, who had suffered various episodes of symptomatic hypoglycemia with no obvious cause. In this case, the patient showed a remarkable acanthosis nigricans and high glucose variability. Severe hyperinsulinemia and very low serum glucose levels were simultaneously found, with normal C peptide. Nonetheless, anti-insulin antibodies and the exhaustive study for hyperinsulinism were negative. Frequent hospitalizations in relation to severe respiratory infections ended-up with a combined therapy of high-dose corticotherapy and gammaglobulins. From that moment on, serum insulin levels progressively decreased until normalisation and hypoglycemia eventually disappeared. Pending the results of the anti-insulin receptor antibodies (sent to an international laboratory) to confirm the diagnosis, the clinical picturecould be considered asthe type B insulin resistance syndrome.

Conclusions: Autoimmunity related to insulin or to insulin receptor should be ruled out in order to reach the aforementioned uncommon diagnoses, ensuring a correct clinical management and avoiding an unnecessary and non-effective pancreatic surgery.