FRI567 Insulin Autoimmune Syndrome And Grave’s Disease

Disclosure: A.M. Skariah: None. T. Porter: None. Background: Insulin autoimmune syndrome (IAS), also known as Hirata’s disease, is a rare condition characterized by immune mediated post prandial hypoglycemia, due to presence of high titers of insulin autoantibodies (IAA). Most cases reported in Asian population with strong association with HLA-DR4 and specifically with the DRB1*0406. Clinical case: Patient is 36-year-old Asian female with no significant past medical history got evaluated by primary care physician because of fatigue, weight loss and neck swelling. Her symptoms are consistent with hyperthyroidism, got evaluated and found to have elevated thyroid hormone levels and suppressed TSH. At the time of diagnosis, free T3 2922 pg/dl(230-420pg/dl), free T4 > 7.7 ng/dl (0.9-1.7 ng/dl), TSH < 0.01uIU/ml (3-4uIU/ml), total T3 599 ng/dl (80-195 ng/dl), total T4 19.6Ug/dl (5-11 Ug/dl). Patient was started on methimazole, and beta blocker. Other labs including autoimmune panel were positive for TSI (2.8 with normal <1.3) and thyroid receptor antibody >40 (<15.5 IU/l) confirming Graves' disease. 4 weeks after starting treatment with methimazole, patient was experiencing episodes of hypoglycemia, related to food intake. She checked her blood sugar and the lowest blood sugar she noticed was 53 mg/dl. She had no history of diabetes and never used insulin or any other oral diabetic medications. Insulin levels >1000 uIU/ml (2.6-24.9uIU/ml), insulin antibody levels >625 uU/ml (<5 uU/ml), C-peptide as high as 9.5ng/ml (1.1-4.4 ng/ml), Insulin/C-peptide ratio 105, proinsulin elevated 40.3pmol/l (0.0-10 pg/l), and oral hypoglycemic agent screening negative. With the lab results, diagnosis of Hirata’s syndrome was made, Management discussed with the patient. Since patient still having labs consistent with hyperthyroidism, continued methimazole and started on diet interventions including low-carb diet and including complex carbohydrates in the diet. Patient gradually responded to dietary interventions with decrease episodes of hypoglycemia. Never required acarbose or steroids. Follow-up labs shows that patient is responding decrease in the levels of insulin antibodies 116 uU/ml and insulin levels 19.5 uIU/ml. Patients’ hyperthyroidism responded to methimazole, and dose reduced eventually to 5 mg daily with latest labs of free T4 1.21 ng/dl, Free T3 2.7 pg/ml and TSH 2.010 uIU/ml. Conclusion: Association between methimazole and IAS has been already reported before. When a patient is presenting outside Asian countries with similar symptoms, differential of IAS can be missed due to its rarity. But because of globalization; people from all races are seen in every part of the world. It will be beneficial to screen patients for IAS which can decrease cost of work up and treatment, when considering imaging modalities which were included as the part of the work up. Presentation: Friday, June 16, 2023