Insulin Autoimmune Syndrome

Hypoglycemia in a non-diabetic is rare. The causes of hypoglycaemia include endogenous hypoglycaemia. Hiratas disease also called the Insulin autoimmune syndrome is a rare form of hypoglycaemia which is caused by the increase of autoimmunity to insulin- insulin autoantibody, in the absence of insulin injection history. Hirata et al first reported a patient with insulin autoimmune syndrome in 1970. The highest prevalence is in Japan. The incidence being one in a year.

We present 3 cases of autoimmune hypoglycaemia encountered over the last two years of 2019-2021.

Case Description:

Case 1: 54-year-old lady, presented with generalized weakness, pins and needle sensation of both feet, excessive sweating for the past 1 month. After several visits to physicians she was found to have a blood glucose of < 60mg% on many occasions. These were not restricted to any time of the day. No history of drug intake. She was not a diabetic or hypertensive with no family history of the same. The protocol was followed and she went into hypoglycemia after 25 hours of fasting.

Case 2: 52-year-old lady presented with recurrent episodes of fatigue with tremors on evaluation glucose was less than 60 mg/dl. These episodes were typically post prandial. History of diabetes, etc., intake, etc. The protocol was followed and she went into hypoglycemia after 9 hours of fasting.

Case 3: 66-year-old lady presented with episodes of fatigue with unconsciousness which on evaluation the blood glucose was less than 50 mg/dl. The episodes occurred at time of the day. The protocol was followed and she went into hypoglycemia after 3 hours of fasting.

Physical examination: All patients had a slightly higher body mass index (BMI). 2 of the 3 patients were overweight with one patient being obese. The other physical examination of blood pressure and other vitals were normal.

The baseline labs of HbA1c, TSH, creatinine and Cortisol were normal.

The Insulin levels, C peptide and insulin antibodies were all raised at the time of hypoglycemia Insulin ranged from 1250 to 1530 micro IU/ml(N-2.6-24.9) C peptide ranged from 4.18 to 8.17 (N-0.78-5.19) and insulin antibodies were 90 to >100 mCu/ml (N < 5).

Discussion:

If the person has hypoglycaemia one has to evaluate for the exogenous or endogenous causes of hypoglycemia. Autoimmune syndrome or HIRATAs disease should be an important differential in the diagnosis of this problem.

Our patient population was all in women. This has not been noted before if the disease has a predilection for women. It is known that autoimmune problems happen more in women. The age group was also middle age of 52 to 62 years. The weight of all the patients were overweight to obese this has been documented before. This may be due to the anabolic effect of insulin or an overeating as a preventive mechanism. The hypoglycemic episodes were more post prandial in all the patients but 2 of the 3 patients had fasting hypoglycaemia also. This is different from reports were post prandial hypoglycmeia are most common.

The diagnosis was made by testing the levels of insulin, C-peptide and insulin antibodies in the state of hypoglycaemia and the high levels of insulin c peptide and insulin autoantibodies were consistent like the other reports.