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- Title
Dilated Cardiomyopathy in a Fila Brasileiro with Hypothyroidism Secondary to Lymphocytic Thyroiditis.
- Authors
Pöppl, Alan Gomes; da Silva Nunes, Nilson Júnior; Matheus, Juliana Pereira; Machado, Letícia; de Faria Valle, Stella; Pavarini, Saulo Petinatti
- Abstract
Background: Hypothyroidism is a common disease in middle-aged purebred dogs and is characterized by reduced plasma concentrations of thyroid hormones. These hormones have important modulatory effects on myocardial chronotropism and inotropism, and when heart disease is linked to hypothyroidism, disease progression may be accelerated. Dilated cardiomyopathy (DCM) often occurs in association with hypothyroidism. However, an etiologic contribution of lower thyroid hormone concentrations towards the development and progression of DCM is still unclear. The aim of this study was to describe a case of DCM in a Fila Brasileiro dog with hypothyroidism secondary to lymphocytic thyroiditis. Case: A male, 11-year-old Fila Brasileiro dog was referred to the Division of Endocrinology and Metabolism of the Veterinary Clinical Hospital of the Universidade Federal do Rio Grande do Sul due to keratoconjunctivitis sicca, weight gain, apathy, and hyporexia. A primary diagnosis of hypothyroidism was made based on clinical features of hypothermia (37.8°C), bradycardia (78 bpm) with bradysphygmia, facial myxedema, bilaterally symmetrical alopecia, and hyperpigmentation of the skin with tail involvement associated with normocytic hypochromic anemia (RBC 4.76 x106/mm3, Ht = 29% and Hb = 9.2 g/dL), reduced concentration of biphasic free T4 (0.22 ng/mL - reference value 0.62 - 3.11 ng/mL) and high level of cTSH (0.81 ng/mL - reference values 0.05 - 0.5 ng/mL), despite total cholesterol concentration within reference values (242 mg/dL). Oral therapy with synthetic levothyroxine (5 μg/kg) was initiated and weekly adjusted until a total daily dose of 22 μg/kg was reached. After three weeks, the patient was found dead by his owners after feeling extremely apathetic, anorexic, and adipsic the day before. At necropsy, there were congestive heart failure features such as ascites associated with liver and pulmonary congestion and an enlarged and globose heart with bilateral ventricular dilatation and whitish areas in the myocardium. Both thyroids were pale and small. Histopathological examination of the heart and thyroid showed adipocyte infiltration associated with fatty degeneration in the myocardium and marked lymphocyticplasmacytic thyroiditis, respectively. Discussion: All of the clinical and laboratory features presented by this dog were in complete agreement with the clinical and pathological features of canine hypothyroidism, except for total cholesterol concentrations within reference values. Although hypothyroidism is recognized as a metabolic dysfunction that may worse a preexisting heart disease and is often associated with DCM, some studies fail to show a relationship between these diseases. The fact that the majority of giant dogs that develop DCM actually have a form of disease associated with atrophy and decreased concentration of myofibrils is straightforward, with a possible link between hypothyroidism and the etiology and/or progression of DCM in this case, once fatty degeneration of muscles is a common feature of chronically reduced thyroid hormones concentration exposure. It might also be observed that primary hypothyroidism was undoubtedly confirmed by the hormone panel blood tests and histopathological analysis. Therefore, the present report provides evidence of and is in agreement with the possible role of hypothyroidism in the pathogenesis and progression of DCM in dogs. Moreover, attention should be paid during initial thyroxine supplementation in senior dogs with hypothyroidism, thereby allowing for the early identification of any other occult disease and occasional adverse effects of medication associated with poor outcomes.
- Subjects
DILATED cardiomyopathy; DOG diseases; THYROID hormones; AUTOIMMUNITY
- Publication
Acta Scientiae Veterinariae, 2015, Vol 43, p1
- ISSN
1678-0345
- Publication type
Case Study