HYPERCHOLESTEROLEMIA AS A LABORATORY INDICATOR OF HYPOTHYROIDISM: A CASE REPORT

Abstract

Hypothyroidism is a common endocrinopathy in middle-aged dogs, characterized by decreased production of thyroid hormones, which are responsible for regulating metabolism and influencing multiple organ systems. Among the laboratory abnormalities, hypercholesterolemia stands out as a frequent finding. This report describes the case of a six-year-old female Ovelheiro Gaúcho dog presenting with weight gain without increased food intake, mammary nodules, and mild hair thinning. Laboratory evaluations revealed persistent hypercholesterolemia, increased alanine aminotransferase and alkaline phosphatase activities, elevated urine specific gravity, and mild normocytic normochromic anemia. Ultrasonographic examination demonstrated hepatopathy and ovarian cysts, leading to ovariectomy and removal of the mammary nodules. Despite ovariectomy, clinical signs and dyslipidemia persisted, with continued hypercholesterolemia and development of hypertriglyceridemia. Given the suspicion of an endocrinopathy, hormonal assays were performed, including TSH, total T4, free T4 by equilibrium dialysis, and basal cortisol, confirming hypothyroidism. Treatment with sodium levothyroxine was initiated, with dose adjustment according to clinical and laboratory response. Progressive clinical improvement and hormonal normalization were observed, highlighting hypercholesterolemia as the main laboratory indicator of the disease.