The Role of Hypothyroidism in the Etiology and Progression of Dilated Cardiomyopathy in Doberman Pinschers

Abstract

BackgroundHypothyroidism and dilated cardiomyopathy (DCM) are both common diseases in Doberman Pinschers. A possible influence of hypothyroidism on the etiology and progression of DCM is controversial.ObjectivesEvaluation of the role of hypothyroidism in etiology and progression of DCM.AnimalsA total of 175 Doberman Pinschers.MethodsIn this longitudinal prospective study, echocardiography and 24‐hour ambulatory ECG recordings were performed in all dogs as screening tests for DCM. Total thyroxine (TT4) and thyroid ultrasonography served as initial screening tests for hypothyroidism and low TT4 values were followed up by a thyroid stimulating hormone (TSH) test or free total thyroxine (fT 4)/cTSH measurements. Additionally, a follow‐up study of dogs affected by both DCM and hypothyroidism under optimal treatment for hypothyroidism was conducted.ResultsA total of 107 dogs were healthy, 45 dogs had DCM, 11 hypothyroidism, and 12 dogs had both DCM and hypothyroidism. TT 4 values as well as the thyroid volumes were equivalent in the healthy dogs and in those with DCM. Neither ventricular premature complexes nor echocardiographic parameters differed between healthy and hypothyroid dogs. Dogs with DCM had a 2.26‐fold (CI0.95 = 1.1–4.8) higher risk of also being affected by hypothyroidism. Despite optimal thyroid treatment of dogs with hypothyroidism and DCM, there was a progression of the heart disease.Conclusions and Clinical ImportanceThis study did not confirm a role of hypothyroidism in the etiology or progression of DCM. Treatment of hypothyroidism did not improve the clinical outcome.

Electrocardiographic and echocardiographic evaluation in dogs with hypothyroidism before and after levothyroxine supplementation: A prospective controlled study

“…Based on our results, this assumption likely should be reconsidered. Our findings are similar to those of a recent study focused on the evaluation of the relationship between hypothyroidism and DCM in Doberman Pinschers . In that study, a cause‐effect relationship between the 2 diseases could not be identified, and the authors stated that hypothyroidism does not play any role in the etiology and progression of DCM .…”

“…However, these cases were only sporadic compared to the overall prevalence of hypothyroidism in dogs . It also must be considered that the diagnosis of hypothyroidism in dogs is often challenging, and the risk of misdiagnosing hypothyroidism in dogs with non‐thyroidal illness syndrome is a major concern . Dogs enrolled in our study represented a large cohort of hypothyroid dogs that were managed identically.…”

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

“…Additionally, robust statistical designs that look at the effect of single dietary components, in controlled environments, with robust outcomes related to metabolism will allow for an understanding of potential disease etiology. This review covers the various etiologies known to cause DCM in dogs, including genetics, hypothyroidism, myocarditis, chronic tachycardia, and certain known dietary deficiencies ( Phillips and Harkin, 2003 ; Sanderson, 2006 ; Wess et al, 2010b ; Beier et al, 2015 ; Hallman et al, 2019 ; Vollmar et al, 2019 ). It also includes other potential diet-associated etiologies that have been recently suggested ( Santilli et al, 2017 ).…”

Hypothyroidism Associated with Echocardiographic Abnormalities

“…It is well known how simply by treating hypothyroidism using thyroxin any disease incurred by the disorder such as cardiomyopathy or pericardial effusion would no longer be of much concern [19,20].…”