Endocrine Abstracts

Introduction: Graves’ disease is a common condition which is usually treated with antithyroid drugs like carbimazole and propylthiouracil. Here we present a patient who developed severe hypoglycaemia after treatment with carbimazole for hyperthyroidism which is unusual in Indian population.

Case report: A 31-year-old male Indian presented to Endocrine Clinic with typical signs and symptoms of thyrotoxicosis. His biochemistry showed FT₃: 28.16 pg/ml (1.8–4.6), FT₄: 20.5 ng/dl (0.93–1.7), TSH: 0.005 μIU/ml (0.27–4.2) and random blood sugar was 90 mg/dl. Technetium thyroid scan showed high uptake of 13.4% and Graves’s disease was confirmed, following which he was treated with carbimazole and propranolol. Two weeks later the patient presented to hospital with unconsciousness, frothy discharge from mouth, seizures and sweating. Severe hypoglycaemia confirmed with blood sugar of 29 mg/dl. In the hospital he had repeated episodes of hypoglcyaemia which was treated symptomatically. Further investigation revealed normal cortisol level but his inulin level was elevated at >1000 pmol/l, when his blood sugar was 43 mg/dl. His antiinsulin antibody was also elevated at >300 U/ml (positive >18). He was found to have insulin autoimmune syndrome (IAS, Hirata’s Disease) induced by antithyroid medication carbimazole. He was taken off the carbimazole and treated with radioactive iodine therapy. Within a few months he was rendered asymptomatic.

Conclusion: Insulin autoimmune syndrome is a quite rare condition and associated with a strong genetic predisposition. The first case was reported in 1970 by Hirata and majority was reported from Japan and it has not been reported in Indian population. Underlying autoimmune disorders or exposure to specific drugs were presumed to be responsible for the development of insulin autoimmune syndrome especially sulphydril drugs such as methimazole, alpha mercaptopropionyl glycine, and gluthatione, hydralazine, isoniazide, procainamide, and penicillin. It is important to recognize the condition at the earliest and treat appropriately.