Dilated cardiomyopathy in a fila brasileiro with hypothyroidism secondary to lymphocytic thyroiditis

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 (37.8C), 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...