Breed distributions for diabetes mellitus and hypothyroidism in Norwegian dogs

Abstract

Background: Diabetes mellitus (DM) and hypothyroidism are common canine endocrinopathies. Both canine DM and primary hypothyroidism are assumed to originate from autoimmune destruction of the respective endocrine glands and have been associated with the major histocompatibility complex (MHC) gene region. This study aims to investigate breed distributions for DM and hypothyroidism in the Norwegian canine population by calculating odds ratios (OR) from two different comparator groups.

Methods: Results from canine serum samples submitted from 2001 to 2018 to the Veterinary Clinical Pathology Laboratory (VCPL) at the Faculty of Veterinary Medicine, Norwegian University of Life Sciences for analysis of fructosamine and thyroid hormones in serum were used as cases in a retrospective bivariate analysis of canine breeds. The ORs were calculated as a measure of risk for the included breeds, where all the submitted blood samples to the VCPL and dogs registered in the Norwegian Kennel Club (NKK), the national organization for dog owners, were used as two comparator groups.

Results: Significant differences in disease prevalence between breeds were discovered using both comparator groups. Australian terrier, Swedish lapphund, Samoyed, and Schipperke were at highest risk for DM. German Shepherd, Golden retriever, German pointing dog, and Collie presented as the breeds with lowest risk for DM. For hypothyroidism, Schnauzer, Eurasier, Dunker, and English setter were at highest risk for developing the disease. The breeds at lowest risk of developing hypothyroidism were Rottweiler, Dachshund, German shepherd, and Border collie. The results from the different comparator groups gave different ORs and ranks, but the breeds with highest and lowest odds showed the same susceptibility using both comparators.

Conclusions: These findings support that there are breeds more and less prone to develop DM and hypothyroidism. A strong genetic predisposition involved in the aetiology of these two diseases is therefore likely. Interestingly, there also appeared to be an inverse relationship of odds for the two diseases for some of the breeds since some breeds that had a high OR for DM or hypothyroidism had a lower OR for the other disease. This indicates that there may be different risk alleles/haplotypes for the two diseases. The possible aetiological relationship between canine DM and hypothyroidism should be further investigated.

Keywords: Autoimmune endocrinopathies; Breed distribution; Canine; Diabetes mellitus; Hypothyroidism.

Fig. 1

A Inclusion of dogs with fructosamine concentrations compatible with diabetes mellitus. B Inclusion of dogs with TSH and Free T4 concentrations compatible with hypothyroidism

Fig. 2

Odds ratio (OR) values for diabetes mellitus and hypothyroidism with a corresponding forest plot. OR values with 95% confidence interval of the breeds that had ≥10 cases for both diseases with a corresponding forest plot. P-values for the OR calculations are marked with * ≤ 0.05, ** ≤ 0.01, and NS (not significant) > 0.05. Diabetes mellitus is marked with orange and hypothyroidism is marked with blue in the forest plot. The dots express the OR, and the lines represent the 95% confidence interval. The breeds highlighted with bold text and marked dots in the forest plot show a tendency of an opposite risk for the two diseases. The number of cases for the diseases per breed are listed in the table