Endocrine Abstracts

Introduction: Hirata Syndrome (SH) is a rare cause of autoimmune hypoglycemia, characterized by elevated circulating insulin levels without concomitant increase in C-peptide, anti-insulin antibodies positivity and pancreas alterations absence in patients never exposed to exogenous insulin. It is also known as insulin autoimmune syndrome (IAS) and is a relatively rare cause of spontaneous hypoglycemia. The syndrome was first described in 1970 by Yukimasa Hirata in Japan, the country where the highest number of cases was subsequently recorded.

Case report: 77-year-old woman came to the emergency room for an episode of profuse sweating and aphasia. -for two months she had frequent lipothymic episodes for which she had undergone cardiological tests, the results of which were normal. Blood sugar levels were found to be 27 mg/dl on blood chemistry tests, whereby 10% glucose solution was administered, reaching glycemic values at the lower limits of normality, making it impossibile to reduce or suspend therapy. Abdominal CT and echoendoscopy were negative for pancreatic lesions and hypoadrenalism was excluded (ACTH: 20 pg/ml, cortisolemia: 10.7 mg/dl). Fasting test was started: after 3 hours, the patient complained of sweating and tremor, with concomitant findings on blood tests: glycemia 29 mg/dl, insulinemia: 747 microU/ml, c-peptide: 4.9 mg/l, anti-insulin Ab: 11 U/ml (nv.:<2.4). Autoimmune hypoglycemia was diagnosed, and patient started steroid therapy with prednisone 25 mg/day. The patient started flash glucose monitoring, showing an adequate response to steroid therapy, with progressive reduction of hypoglycemic episodes and normalization of glycemic levels. The patient was discharged, and at the endocrinological visit after one month steroid tapering was possible, according to the glycemic values.

Conclusion: Autoimmune forms of hypoglycemia are rare among Caucasians but should be taken into consideration in the setting of unsuppressed insulin levels, to avoid misdiagnosis of insulinoma. Treatment involves primarily the use of corticosteroid therapy or, in more severe cases, greater immunosuppressive drugs such as azathioprine. In extreme cases plasmapheresis can be necessary.