Breed, Coat Color, and Hair Length as Risk Factors for Hyperthyroidism in Cats

Abstract

BackgroundHyperthyroidism is very common in older cats, but the etiopathogenesis is poorly understood. Decreased risk of hyperthyroidism has been reported in certain colorpoint breeds, and this observation previously has been hypothesized to result from relatively greater tyrosine availability for thyroid hormone production because of limited ability to convert tyrosine to melanin pigment. However, studies investigating a potential link between coat pigmentation and risk of hyperthyroidism are limited.ObjectiveTo identify associations between coat phenotype and hyperthyroidism by investigation of breed, coat color, and hair length as risk factors for the disease.AnimalsData were used from 4,705 cats aged ≥10 years, referred to a single veterinary teaching hospital (2006–2014) in the United Kingdom.MethodsRetrospective, epidemiological, cross‐sectional study using Bayesian multivariable logistic regression to assess risk factors for hyperthyroidism.ResultsBurmese (odds ratio [OR], 0.01; 0.00–0.23; P = .004), Tonkinese (OR, 0.05; 0.00–0.95; P = .046), Persian (OR, 0.21; 0.10–0.44; P < .001), Siamese (OR, 0.27; 0.12–0.61; P = .002), Abyssinian (OR, 0.04; 0.00–0.74; P = .031), and British shorthair (OR, 0.47; 0.28–0.79; P = .004) breeds had decreased risk of hyperthyroidism compared to domestic shorthairs. Longhaired, nonpurebred cats (OR, 1.30; 1.03–1.64; P = .028) were at increased risk of hyperthyroidism. Coat color/pattern was not associated with hyperthyroidism in nonpurebred cats.Conclusions and Clinical ImportanceWe identified decreased risk of hyperthyroidism in the Tonkinese, Abyssinian, and British shorthair breeds, identified an association between risk of hyperthyroidism and hair length, and confirmed decreased risk in Burmese, Siamese, and Persian breeds. Additional studies are warranted to further investigate these findings.

Prevalence, clinical and epidemiological features of feline hyperthyroidism at a veterinary teaching hospital in Brazil: a retrospective study

“…When comparing breeds, we found that mixed-breed cats were more likely to present hyperthyroidism. A higher incidence in crossbreeds has also been detected in other studies (CROSSLEY et al, 2017).…”

“…Six cats affected by hyperthyroidism consumed wet food either exclusively or in combination with other food types. Canned wet food is rich in substances that can act as endocrine disruptors and may present inadequate iodine concentrations (CROSSLEY et al, 2017). Hence, several studies have demonstrated that cats fed canned commercial diets are more prone to develop hyperthyroidism (IKEDA et al, 2000;CROSSLEY et al, 2017;PAULELLI et al, 2018).…”

“…Canned wet food is rich in substances that can act as endocrine disruptors and may present inadequate iodine concentrations (CROSSLEY et al, 2017). Hence, several studies have demonstrated that cats fed canned commercial diets are more prone to develop hyperthyroidism (IKEDA et al, 2000;CROSSLEY et al, 2017;PAULELLI et al, 2018). In Brazil, wet food is not the most common type of food consumed (CROSSLEY et al, 2017).…”

Risk-Factor Analysis for Feline Hyperthyroidism in the Metropolitan Area of Porto Alegre: A Pilot Case-Control Study

“…In addition, other studies have found evidence that this contamination is greater in pop-top cans [7,18,19]. It is worth mentioning that studies in rats have demonstrated that the main route of elimination of ingested BPA is through hepatic glucuronidation [20], which is greatly reduced in cats making this animal extremely sensitive to the adverse effects of many drugs and toxins that require glucuronidation before elimination [3]. Thus, slower clearance may lead to higher-than-expected BPA blood and tissue levels in cats [7].…”

“…The fact that the several variables surveyed had 95% confidence intervals extremely wide, even though not significant, emphasizes the potential importance of these factors, so that the enlargement of the sample size could help to clarify this bias. The lower mean age of the control group, as well as the higher percentage of euthyroid cats between 8 and 12 years of age, may also have been a limiting factor, since most studies point to a mean age of diagnosis of feline hyperthyroidism among 12 and 13 years [1,3,[20][21][22].…”