SUN-624 Not So Sweet After All: A Rare Encounter with Hirata Disease.

Abstract Disclosure: M. Acharekar: None. K. Reddy: None. Introduction: Insulin autoimmune syndrome (aka Hirata disease) is a rare cause of hypoglycemia. It is marked by spontaneous episodes of hypoglycemia with no exposure to exogenous insulin. The majority of cases occur within Japanese population. Identification of this condition is crucial to avoid unneeded testing and procedures. Case Description: A 32 year old female with a history of Hashimoto's thyroiditis, recurrent hypoglycemia and uncontrolled seizures, but no history of insulin or insulin secretagogues presented to clinic for an evaluation of her recurring hypoglycemic episodes. She complained of multiple postprandial hypoglycemia episodes. Labwork showed normal TSH and ACTH levels but elevated insulin autoantibodies and C peptide. Imaging, including a CT abdomen and an MRI brain were unremarkable except small lesion in the posterior pituitary. She was initially urged to eat small, frequent, sugar-free meals with a follow up consultation with a nutritionist to create a strategy for controlling her hypoglycemia. She was unable to follow this plan, given socioeconomic issues. As a result, continuous glucose monitoring (CGM) was started with prednisone to help raise her glucose levels. Her symptoms gradually improved with this strategy, although she continued to experience sporadic hypoglycemia spells. Levothyroxine was initiated because of her autoimmune thyroid illness and its possible effects on glucose metabolism. She continues to struggle with adhering to dietary choices and consistent CGM use. Discussion: Insulin Autoimmune Syndrome (IAS) is a rare disease marked by hypoglycemia episodes driven by high levels of insulin autoantibodies (IAA). IAS is 10-30 times common among people of Japanese, Korean ancestry and is associated with HLA class II allele. On the other hand, IAS is frequently linked to other autoimmune disorders in non-Asian people. The hypoglycemic episodes in IAS occur because large quantities of IAA bind to insulin, rendering it initially ineffective. Postprandial hyperglycemia is the outcome, and it triggers the synthesis of more insulin and C-peptide. Once insulin levels exceed binding capacity of the IAA, hypoglycemia develops. Furthermore, free insulin contributes to more severe and protracted hypoglycemia when dissociation takes place. Conclusion: Our case highlights a rare cause of endogenous hyperinsulinemic hypoglycemia. Any patient who presents with postprandial hypoglycemia, an abnormally high insulin concentration, and moderately elevated pro insulin and C peptide readings should be suspected of having IAS. Insulin autoantibodies in the blood are used to confirm the diagnosis of IAS. Since IAS is typically self limiting, management primarily involves supportive measures, such as dietary modifications. However, in situations with severe symptoms, immunosuppressive medications to decrease pancreatic insulin output may be required. Presentation: Sunday, July 13, 2025