[Recurrent hypoglycemia in the insulin autoimmune syndrome]

Frequent reoccurrence of hypoglycemia in a type 2 diabetic patient with insulin antibodies

BACKGROUND

Insulin antibody (IAb) may be produced in patients receiving long-term, animal-derived insulin, leading to insulin resistance or hypoglycemia. There have been very few reports of hypoglycemia caused by IAb in patients taking recombinant human insulin.

CASE REPORT

We report the case of an 82-year-old male patient with type 2 diabetes mellitus who suffered repeated episodes of severe hypoglycemia-related symptoms (including coma) prior to admission. The patient had been taking Novolin 30R, a premixed human insulin. The patient's IAb level was markedly elevated, and hypoglycemia caused by recombinant human insulin treatment-induced IAb production was diagnosed. Acarbose and metformin were prescribed, and the patient recovered uneventfully. The patient ceased taking these medications, and he was subsequently treated with recombinant human insulin to combat hyperglycemia. This was followed by reoccurrence of hypoglycemic coma. The patient was advised to avoid taking recombinant human insulin for the rest of his life and to control hyperglycemia with acarbose and metformin.

CONCLUSIONS

Although rare, hypoglycemia caused by recombinant human insulin-induced IAb production should be considered in patients with type 2 diabetes who experience repeated episodes of hypoglycemia.

Autoimmune forms of hypoglycemia

Autoimmune syndromes are a rare cause of hypoglycemia characterized by elevated levels of insulin in the presence of either anti-insulin antibodies (insulin autoimmune syndrome) or anti-insulin receptor antibodies (type B insulin resistance). Insulin autoimmune syndrome is the third leading cause of hypoglycemia in Japan, but has rarely been described in the non-Asian population.In the current study, we report the clinical and biochemical characteristics and clinical course of 2 white patients with insulin autoimmune syndrome, and present a literature review of non-Asian patients reported with insulin autoimmune syndrome. Also, we describe the clinical and biochemical characteristics of patients reported in the literature with type B insulin resistance who manifested hypoglycemia. We compare the clinical and laboratory features of insulin autoimmune syndrome and type B insulin resistance with each other and with other forms of hyperinsulinemic hypoglycemia.Autoimmune forms of hypoglycemia are uncommon. However, they should be considered in any patient with hypoglycemia in the setting of unsuppressed insulin levels associated with anti-insulin or anti-insulin receptor antibodies. Making the correct diagnosis may spare a hypoglycemic patient from an unnecessary pancreatic surgical procedure.

Insulin Autoimmunity and Hypoglycemia in Seven White Patients

OBJECTIVE

To report the clinical, biochemical, and immunologic characteristics of 7 white patients with the rare disorder of hyperinsulinemic hypoglycemia in association with spontaneously generated high titers of antibodies to human insulin.

METHODS

We reviewed the clinical data, history, and symptoms of the 7 study patients and summarized the biochemical findings during a spontaneous episode of hypoglycemia. Insulin antibody binding was measured in all patients, and antibody affinity, capacity, and clonality were analyzed in 4. A mixed meal study was conducted in 2 patients. A potential mechanism for postprandial hypoglycemia is presented.

RESULTS

In all 7 patients (6 women and 1 man), symptoms were neuroglycopenic, occurring primarily postprandially but during fasting in some patients. During hypoglycemia, concentrations of insulin, proinsulin, and, in most patients, C peptide considerably exceeded those observed in patients with insulinoma. These concentrations were spuriously elevated as a result of interference by the autoantibodies in the immunoassays. No patient had evidence of an insulinoma on various radiologic localization procedures directed at the pancreas. Insulin antibodies showed a high percentage of binding to human insulin--50 to 90%. Heterogeneity of antibodies regarding clonality and antibody binding sites was noted; some patients had polyclonal and some had monoclonal IgG class antibodies. Most patients had two categories of binding sites: high affinity/low capacity and low capacity/high affinity. Although the mechanism for postprandial hypoglycemia remains conjectural, prolonged elevations of postprandial concentrations of total and free insulin are consistent with the putative mechanism of a buffering effect of insulin antibodies.

CONCLUSION

Insulin autoimmune hypoglycemia, although rare in any racial group and especially in white subjects, can be readily detected by high titers of insulin antibodies. Such a determination should be done in all patients undergoing evaluation for hypoglycemia.