Recognition Pattern of Thyroglobulin Autoantibody from Hypothyroid Dogs to Tryptic Peptides of Canine Thyroglobulin

A scoping review of autoantibodies as biomarkers for canine autoimmune disease

Background

Autoantibody biomarkers are valuable tools used to diagnose and manage autoimmune diseases in dogs. However, prior publications have raised concerns over a lack of standardization and sufficient validation for the use of biomarkers in veterinary medicine.

Objectives

Systematically compile primary research on autoantibody biomarkers for autoimmune disease in dogs, summarize their methodological features, and evaluate their quality; synthesize data supporting their use into a resource for veterinarians and researchers.

Animals

Not used.

Methods

Five indices were searched to identify studies for evaluation: PubMed, CAB Abstracts, Web of Science, Agricola, and SCOPUS. Two independent reviewers (AET and ELC) screened titles and abstracts for exclusion criteria followed by full‐text review of remaining articles. Relevant studies were classified based on study objectives (biomarker, epitope, technique). Data on study characteristics and outcomes were synthesized in independent data tables for each classification.

Results

Ninety‐two studies qualified for final analysis (n = 49 biomarker, n = 9 epitope, and n = 34 technique studies). A high degree of heterogeneity in study characteristics and outcomes reporting was observed. Opportunities to strengthen future studies could include: (1) routine use of negative controls, (2) power analyses to inform sample sizes, (3) statistical analyses when appropriate, and (4) multiple detection techniques to confirm results.

Conclusions

These findings provide a resource that will allow veterinary clinicians to efficiently evaluate the evidence supporting the use of autoantibody biomarkers, along with the varied methodological approaches used in their development.

Etiopathologic Findings of Canine Hypothyroidism

The causes of canine hypothyroidism are varied, but most cases result from irreversible acquired thyroid pathologic changes and only a small proportion arise from congenital anomalies of the thyroid gland or pituitary. Of primary thyroid failure, at least half is the result of immune-mediated thyroiditis. Recent research has focused on the genetics and immunology of canine thyroid disease, adding to what is known from experimental and human studies. Epidemiologic and diagnostic laboratory studies continue to provide information on contributing factors and raise questions for future research directions. Serum antibodies against thyroid components are common in thyroid pathologic conditions and dysfunction, and understanding their properties and frequency is important in the interpretation of thyroid diagnostic test results.

Adipsic Hypernatremia in a Dog with Antithyroid Antibodies in Cerebrospinal Fluid and Serum

A 4-year-old, male Labrador retriever, weighing 27 kg, presented with abrupt clinical signs including mental retardation, circling and head pressing. The dog never ingested water by choice. An adipsia of the dog was persisted and developed to hypernatremia with artifactual hyperchloremia. Serial endocrine results and image findings were suggestive of a hypothyroidism. The dog revealed the presence of antithyroid antibodies in the cerebrospinal fluid and serum. With the administration of levothyroxine sodium, his neurologic signs were alleviated within the first week of treatment and adipsia was also resolved.

Comparative dermatology—canine endocrine dermatoses

Endocrine diseases in the dog commonly manifest with dermatological lesions. Hypothyroidism is the most common endocrinopathy and usually presents with alopecia in areas of wear, seborrhea, and recurrent infections. Common clinical signs associated with hyperadrenocorticism include polyuria, polydipsia, and polyphagia. The most common dermatological manifestation of hyperadrenocorticism is bilaterally symmetrical alopecia sparing the head and distal extremities. Pyoderma is a common finding associated with immunosuppression. Less commonly, calcinosus cutis may occur. Sex hormone excess, primarily hyperestrogenism and hyperandrogenism, may also be associated with dermatological signs. Usually, dogs are intact, and the excess production is due to testicular or ovarian neoplasia.

Proliferative Responses to Canine Thyroglobulin of Peripheral Blood Mononuclear Cells from Hypothyroid Dogs

The immune responses of hypothyroid dogs to canine thyroglobulin (cTg) were evaluated for the proliferative ability of peripheral blood mononuclear cells (PBMC). PBMC from three hypothyroid dogs with high titers of thyroglobulin autoantibody (TgAA) and 3 clinically normal dogs were cultured with 5, 10, or 20 microg/ml of cTg for 72 hr. The proliferative responses of the cells were determined by the level of incorporated BrdU. The numbers of cells expressing Thy-1, CD4, CD8 and IgG in the PBMC were counted by the immunofluorescence method. Proliferative responses to cTg were observed in the cells from hypothyroid dogs. The number of cells expressing IgG and CD8 in the hypothyroid dogs tended to be high compared with the clinically normal dogs. The CD4+ cells in cultures from hypothyroid dogs increased depending upon the amount of cTg. There was a significant (P<0.05) positive correlation between the number of CD4+ cells and the concentration of cTg in the cultures from hypothyroid dogs. These findings suggest a possible relationship between canine hypothyroidism and cellular immunity. Loss of self tolerance to thyroid antigens in CD4+ T cells may play an important role in the development of canine hypothyroidism.