Canine endocrinopathies associated with hormone deficiency, including hypothyroidism, hypoadrenocorticism and some cases of diabetes mellitus are believed to result from autoimmune destruction of endocrine tissue. Multiple endocrinopathies can occur in the same animal, which is more likely to indicate immune-mediated disease and which might be comparable to autoimmune polyendocrine syndrome type 2 in human beings. The only commercially available serological assay for endocrine autoimmunity in dogs is that for canine thyroglobulin autoantibodies (TGAA), sometimes used as part of diagnostic testing for hypothyroidism. It is, however, possible that subclinical thyroid autoimmunity occurs in some dogs diagnosed with either diabetes or hypoadrenocorticism. The aim of the current study was to determine the prevalence of TGAA in dogs diagnosed with various endocrinopathies.

Serum samples were obtained either from clinical cases referred to the Queen Mother Hospital for Animals, following completion of diagnostic testing, or recruited for the UK canine diabetes archive at the Royal Veterinary College. Dogs with no clinical evidence of endocrine deficiency were selected as controls. Serum samples from dogs with diabetes mellitus (n = 50), hypoadrenocorticism (n = 15), hypothyroidism (n = 2) and multiple endocrinopathies (n = 8) were tested for reactivity to thyroglobulin. Initially, serum samples were screened for the presence of antibodies against porcine thyroglobulin by enzyme-linked immunosorbent assay (ELISA). Selected samples were then further assessed using the commercially-available canine TGAA ELISA (Oxford Laboratories).

Some dogs that reacted strongly to porcine thyroglobulin failed to demonstrate reactivity to canine thyroglobulin. Two control dogs were positive for TGAA; one a healthy GSD blood donor, the other a Golden Retriever that presented with idiopathic transient hypoglycaemia. The presence of TGAA in these two dogs might indicate subclinical thyroid autoimmunity. Only one of the two hypothyroid dogs was positive for TGAA. One of the 50 diabetic dogs and three of the 15 dogs suffering from hypoadrenocorticism were positive for TGAA. None of the eight dogs with multiple endocrinopathies were TGAA positive, despite three of these suffering from hypothyroidism as part of their syndrome. Neither overt hypothyroidism nor TGAA seem to be common in the UK diabetic dog population. The presence of concurrent hypothyroidism with hypoadrenocorticism and the presence of TGAA in other dogs with hypoadrenocorticism might suggest that thyroid autoimmunity is not uncommon in this particular endocrinopathy.