Endocrine Abstracts

Introduction: Autoimmune forms of hypoglycemia are uncommon. However, they should be considered in any patient with hyperinsulinemic hypoglycemia. Here we present a case of persistent hyperinsulinemic hypoglycemia caused by insulin receptor antibodies.

Case report: A 65-year-old chinese woman with mixed connective tissue disease (MCTD) and hypothyroidism presents with a 2-week history of persistent hypoglycemia since discontinuation of her immunosuppresants. A 72 h fast was consistent with hyperinsulinism; serum glucose was 1.1 mmol/l, insulin was 823 pmol/l (normal fasting: <118 pmol/l), c-peptide was 615 pmol/l (normal fastng: 264–1026 pmol/l). Adiponectin was 56 μg/ml (normal: 8.3–13.9 μg/ml). There was no history of insulin use. Screening for plasma sulfonylureas, biguanides, insulin analogs and insulin antibodies were negative. Imaging of the abdomen and pancreas was normal. Given the hyperinsulinism, screening for insulin receptor antibody was performed which confirmed the presence of anti-insulin receptor antibodies. She was diagnosed with Type B insulin resistance and started on immunosuppressants resulting in improvement of her hypoglycemia.

Conclusion: In patients with hyperinsulinemic hypoglycemia, especially in the setting of connective tissue disease, the diagnosis of Type B insulin resistance needs to be considered. In this syndrome, insulin receptor antibodies are present and are either antagonistic or agonistic to the insulin receptor. Typically, patients present with severe hyperglycemia. Initial presentation of persistent hypoglycemia, as in our patient, is rare. The insulin:c-peptide ratio is usually 0.2–0.5. In our case, the insulin:c-peptide ratio was 1.3. Possible explanation includes altered metabolism and degradation of insulin. A paradoxical elevation of adiponectin is seen and may be caused by altered insulin action on adipocytes. The presence of elevated adiponectin can aid in the diagnosis of this rare syndrome. Despite the rarity of this condition, awareness of type B insulin resistance is essential to allow for proper management since treatment usually includes multi- modal immunosuppresion to target pathogenic antibodies, and to prevent unnecessary pancreatic surgery.

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.