Testing for insulin antibodies is mandatory in the differential diagnosis of hypoglycaemia in nondiabetic subjects

Methimazole-induced insulin autoimmune syndrome in Graves' disease with hypokalemia: A case report and literature review

The patient in the present case report, a 27-year-old man, was diagnosed with Graves' disease and hypokalemia. The patient was treated with methimazole and intermittent potassium supplementation. Following treatment, the patient was still suffering from fatigue, accompanied by palpitations, a hand tremor, fear of heat and sweating. Hypoglycemia was revealed by monitoring fingertip blood glucose levels. The laboratory investigations indicated that serum insulin levels were significantly elevated (>1,000 µIU/ml), the test for serum insulin autoantibody (IAA) was positive, and insulin autoimmune syndrome (IAS) was diagnosed. Following symptomatic treatment, the patients insulin levels decreased, and the hypoglycemia episode was gradually relieved. Hypoglycemia may be prone to missed diagnosis in patients with Graves' disease and hypokalemic periodic paralysis. Monitoring fingertip blood glucose level is a convenient and feasible method to detect hypoglycemia. Furthermore, serum insulin and IAA detection should be assessed to exclude or confirm IAS.

Insulin Autoimmune Syndrome - A Case Series

Insulin autoimmune syndrome, or Hirata's disease, is a rare cause of hypoglycaemia. It is characterised by spontaneous episodes of hypoglycaemia, without any exposure to exogenous insulin. The majority of cases are seen in the Japanese population and it is rarely found to affect other ethnicities. The recognition of this disease is important to avoid unnecessary investigations and procedures. Here, we report two cases of insulin autoimmune syndrome, which were diagnosed and managed in our institute.

HLA DRB1*0415: a new possible genetic susceptibility factor for Hirata's disease

CONTEXT

Hirata's disease (HD) is a rare autoimmune cause of hypoglycemia. Patients suffering from this condition have a genetic predisposition, determined by HLA DR4, with some differences in the worldwide population. In Caucasians HLA DRB1*0403 is the most frequent susceptibility background on which some drugs play as triggers.

CASE DESCRIPTION

We reported the case of a woman with several hypoglycemic episodes, characterized by high insulin and c-peptide levels. Biochemical and morphological exams excluded a neuroendocrine tumor. HD was diagnosed according to insulin autoantibodies positivity and patient's history, particularly about drugs taken. The HLA analysis revealed DRB1*0415 allele.

CONCLUSIONS

We found a potential new predisposing factor for HD, HLA DRB1*0415 allele, never described before as genetic background to insulin autoimmune syndrome in Caucasians.

Insulin Autoimmune Syndrome (Hirata Disease): A Comprehensive Review Fifty Years After Its First Description

Insulin autoimmune syndrome (IAS), also named Hirata's disease, is a rare condition characterized by hypoglycemic episodes due to the presence of high titers of insulin autoantibodies (IAA). IAS is a form of immune-mediated hypoglycemia, which develops when a triggering factor (ie, a medication or a viral infection) acts on an underlying predisposing genetic background. IAS pathogenesis involves the formation of insulin-IAA complexes that induce glycemic alterations with a double-phase mechanism: IAA prevent insulin to bind its receptor in the postprandial phase, possibly resulting in mild hyperglycemia; thereafter, insulin is released from the complexes irrespective of blood glucose concentrations, thus inducing hypoglycemia. The diagnosis of IAS is challenging, requiring a careful workup aimed at excluding other causes of hyperinsulinemic hypoglycemia. The gold standard for the definitive diagnosis is the finding of IAA in a blood sample. Because IAS is frequently a self-remitting disease, its management mostly consists of supportive measures, such as dietary modifications, aimed at preventing the development of hypoglycemia. Pharmacological therapies may occasionally be necessary for patients presenting with severe manifestations of IAS. Available therapies may include drugs that reduce pancreatic insulin secretion (somatostatin analogues and diazoxide, for instance) and immunosuppressive agents (glucocorticoids, azathioprine and rituximab). The purpose of this review is to provide a comprehensive analysis of the disease, by describing the burden of knowledge that has been obtained in the 50 years following its first description, took in 1970, and by highlighting the points that are still unclear in its pathogenesis and management.

GLUCOSE CHANGES IN A PATIENT WITH INSULIN AUTOIMMUNE SYNDROME DEMONSTRATED BY CONTINUOUS GLUCOSE MONITORING

Objective

Insulin autoimmune syndrome (IAS) is an unusual cause of hypoglycemia in individuals without underlying diseases. Continuous glucose monitoring (CGM) has rarely been applied for IAS. We present a case of IAS with available 6-day CGM data.

Methods

A 61-year-old Taiwanese man was admitted because of impaired consciousness while driving, caused by a low blood glucose level of 30 mg/dL. He regained consciousness fully after parenteral glucose administration.

Results

During the prolonged fasting test, his C-peptide and insulin levels were respectively 11 ng/mL and 169.34 μIU/mL when plasma glucose was 41 mg/dL. Abdominal magnetic resonance imaging did not show any pancreatic abnormality. His 6-day CGM data revealed fasting hypoglycemia, several instances of postprandial hyperglycemia, and low blood glucose levels before lunch and dinner. Additional diagnostic findings included elevated anti-insulin antibody of 78.2%, thyrotoxicosis due to Graves disease, and gastric ulcer. He was discharged home on prednisolone at 5 mg daily, methimazole at 10 mg daily, and esomeprazole at 40 mg daily. Hypoglycemia and impairment of consciousness did not recur throughout the subsequent year-long follow up.

Conclusion

We proposed a novel approach using CGM coupled with measurements of plasma insulin, C-peptide, and anti-insulin antibodies as the initial investigation for hypoglycemia in non-diabetic subjects. These relatively inexpensive tests may lead to earlier detection of IAS and thus render hospital admission and more costly explorations unnecessary.

Insulin autoimmune syndrome: from diagnosis to clinical management

Autoimmune forms of hypoglycemia are a rare cause of low blood sugar levels among Caucasians, and often go misdiagnosed, exposing patients to lengthy series of pointless, potentially harmful and expensive tests. There are two types of autoimmune hypoglycemia. One is insulin autoimmune syndrome (IAS), which is characterized by hyperinsulinemic hypoglycemia, elevated insulin autoantibody (IAA) titers, no prior exposure to exogenous insulin, and no of pathological abnormalities of the pancreatic islets. This condition is also known as "Hirata's disease". The other is type B insulin resistance syndrome (TBIRS), a rare autoimmune disorder resulting in a broad array of abnormalities in glucose homeostasis-from hypoglycemia to extremely insulin-resistant hyperglycemia-caused by the presence of insulin receptor autoantibodies (IRAbs). This review focuses on these two syndromes, describing their epidemiology, possible genetic background, clinical presentation, pathophysiology, diagnosis and treatment.

Insulin autoimmune syndrome (Hirata’s disease) in an Italian patient: a case report and review of the literature

We describe the case of a 54-year-old Caucasian Italian male experiencing episodes of hypoglycemia, occurring mainly after meals. He had never been exposed to insulin and was taking ramipril, flecainide and acetylsalicylic acid. An oral glucose tolerance test (OGTT) showed high blood glucose levels diagnostic for diabetes mellitus at 120 min and hypoglycemia with inappropriately high insulin levels at 240 min. The 72-h fasting test, abdominal computed tomography (CT) and positron emission tomography-CT were normal. Insulin autoantibodies were positive at high titers, prompting a diagnosis of insulin autoimmune syndrome (IAS). The patient was advised to take frequent, small meals and thus achieved a good control of his hypoglycemic symptoms. After 18 months of this dietary management, his insulin autoantibody levels decreased considerably but remained detectable. During an OGTT, his blood glucose levels at 120 min were now indicative of an impaired glucose tolerance rather than diabetes, and there was improvement in the glucose nadir. The patient had no other clinical or latent autoimmune diseases. Here we discuss the main features of IAS (also known as Hirata’s disease) and review the cases of IAS reported in Italy to date.

The insulin autoimmune syndrome (IAS) as a cause of hypoglycaemia: an update on the pathophysiology, biochemical investigations and diagnosis

Insulin autoimmune syndrome (IAS) is considered to be very rare in Caucasians. Understanding its pathophysiology is paramount in (a) appreciating its potential impact on analyses of pancreatic hormones and (b) explaining its highly variable clinical manifestations in non-diabetic, non-acutely ill patients with indeterminate hypoglycaemia. The underlying aetiology of IAS is the presence of variable affinity/avidity endogenous insulin antibodies in significant amounts. The two types of insulin antibodies namely antibodies which bind insulin and/or proinsulin(s) and receptor antibodies (insulin mimetic) will be discussed. Their biochemical and immunological roles in causing hypoglycaemia will be highlighted. Clinical manifestations of IAS can vary from mild and transient to spontaneous, severe and protracted hypoglycaemia necessitating in extreme cases plasmapheresis for glycaemic control. Antibodies of IAS can interfere in pancreatic immunoassay tests causing erroneous and potentially misleading results. Thorough testing for endogenous insulin antibodies must be considered in the investigations of non-diabetic, non-acutely ill patients with indeterminate and/or unexplained hypoglycaemia.

A possible analytical and clinical role of endogenous antibodies causing discrepant adrenocorticotropic hormone measurement in a case of ectopic Cushing’s syndrome

Heterophilic antibodies are well described, but poorly appreciated interferents and is often not a recognized problem affecting most immunoassays. We report a patient presented with ectopic Cushing’s syndrome (CS), but repeated plasma adrenocorticotropic hormone (ACTH) concentrations conducted by immunoassay were inappropriately within the reference range and not elevated, most probably as a result of antibody interference. A 36-year-old woman, presented with large gastric neuroendocrine carcinoma and severe ectopic CS, while repeated plasma ACTH concentrations conducted by immunoassay were inappropriately within the reference range. As we expected ACTH concentration to be higher, we performed several tests to evaluate whether there was any assay interference causing falsely lower than expected ACTH results. We measured ACTH using a different immunoassay, assayed the sample in dilution, assayed the sample after being incubated in heterophilic antibody blocking agent tube and performed recovery studies. Tests indicated the presence of interfering compounds, most probably heterophilic antibodies. When clinicians find ACTH concentrations to be lower than expected, we recommend the laboratory investigate antibody interference.

Identifying and reducing potentially wrong immunoassay results even when plausible and "not-unreasonable"

The primary role of the clinical laboratory is to report accurate results for diagnosis of disease and management of illnesses. This goal has, to a large extent been achieved for routine biochemical tests, but not for immunoassays which remained susceptible to interference from endogenous immunoglobulin antibodies, causing false, and clinically misleading results. Clinicians regard all abnormal results including false ones as "pathological" necessitating further investigations, or concluding iniquitous diagnosis. Even more seriously, "false-negative" results may wrongly exclude pathology, thus denying patients' necessary treatment. Analytical error rate in immunoassays is relatively high, ranging from 0.4% to 4.0%. Because analytical interference from endogenous antibodies is confined to individuals' sera, it can be inconspicuous, pernicious, sporadic, and insidious because it cannot be detected by internal or external quality assessment procedures. An approach based on Bayesian reasoning can enhance the robustness of clinical validation in highlighting potentially erroneous immunoassay results. When this rational clinical/statistical approach is followed by analytical affirmative follow-up tests, it can help identifying inaccurate and clinically misleading immunoassay data even when they appear plausible and "not-unreasonable." This chapter is largely based on peer reviewed articles associated with and related to this approach. The first section underlines (without mathematical equations) the dominance and misuse of conventional statistics and the underuse of Bayesian paradigm and shows that laboratorians are intuitively (albeit unwittingly) practicing Bayesians. Secondly, because interference from endogenous antibodies is method's dependent (with numerous formats and different reagents), it is almost impossible to accurately assess its incidence in all differently formulated immunoassays and for each analytes/biomarkers. However, reiterating the basic concepts underpinning interference from endogenous antibodies can highlight why interference will remain analytically pernicious, sporadic, and an inveterate problem. The following section discuses various stratagems to reduce this source of inaccuracy in current immunoassay results including the role of Bayesian reasoning. Finally, the role of three commonly used follow-up affirmative tests and their interpretation in confirming analytical interference is discussed.