Endocrinopathies

This chapter describes the various procedures currently used to detect circulating autoantibodies in patients with endocrine disease, i.e., thryoiditis, Graves' disease, insulin-dependent diabetes mellitus, Addison's disease, and pernicious anemia. The general method of indirect immunofluorescence (IF) is the screening test used most frequently to detect tissue- or organ-specific autoantibodies. Commercial hemagglutination kits for thyroglobulin antibodies are less sensitive than the tanned-cell hemagglutination (TCH) test described. Indirect IF performed on sections of human or monkey thyroid can demonstrate antibodies to thyroglobulin, CA2, and microsomes of thyroid epithelial cells, and antinuclear antibodies. The most commonly used tests for determining thyroid peroxidase (TPO) antibodies are indirect IF and commercially available hemagglutination assays or ELISAs. Separate diabetes mellitus categories consist of gestational diabetes and ''specific types of diabetes'' usually with defined mutations or accompanying pathology (e.g., pancreatic abnormalities, endocrinopathies, or drug induced). The current insulin autoantibodies (IAA) assay is not able to distinguish between natural IAA and induced insulin antibodies. The current major format for determination of islet autoantibodies uses fluid-phase radioimmunobinding assays, applied to all three major islet autoantibody tests, including glutamic acid decarboxylase (GAD) autoantibodies (GAA), ICA512AA, and IAA. The majority of sera from type 1 diabetes patients target more than two epitopes on ICA512 molecules, while non-disease-related antibodies usually react with only one epitope. Anti-islet autoantibodies find their primary application in the differential diagnosis of the forms of diabetes and in predicting risk of progression to overt diabetes.