Abstract
Objectives: Doppler Echocardiography has been shown to reflect thyroid hormone action in primary thyroid dysfunction. The aim of the present study was to evaluate the cardiac function after total thyroidectomy in old rats using echocardiographic measures. Methods: Female Wistar rats aged 24 months old (referred to as adult) were divided into 2 groups with 15 animals each: Euthyroid (Eut) and Hypothyroid (Hypo) rats. Hypothyroidism was induced by total thyroidectomy. The plasmatic levels of T3, T4, TSH and free ionic calcium were measured. Echocardiographic analysis was performed using the following parameters: left ventricular end-diastolic (LVED) left ventricular end-systolic (LVES), ejection fraction (EF) and Tei index. Results: In both groups, the LVES ranged from 0.2 to 0.5 p <0.048 and the EF from 50.3 to 45.2 p<0.030.There was not statistically significant difference in HR, LVED and Tei-index values. It was observed decrease in T3 levels (72.0 to 30.4 μg/dl, p<0.001) and T4 levels (3.1 to 0.4 μg/dl, p<0.001) and increase in TSH levels (1.6 to 40.7 mU/mol, p<0.001) in Hypo group. The free ionic calcium levels increased from 0.1 to 0.9 mmol/L (p<0.001) in Hypo group. Conclusion: It was identified a reduction of cardiac function in old animals with hypothyroidism using Doppler- Echocardiography measures. These results indicated that hypothyroidism is associated with impairment in cardiac function in old patients and that Doppler echocardiography, is a useful and noninvasive tool for the diagnosis of cardiac dysfunction induced by this thyroid disorder.
Highlights
Thyroid hormones are essential for the development of several organs and tissues and to maintenance of quality of life
They produce a general increase in carbohydrate, lipid and protein metabolism and are indirectly involved in transcriptional regulation of genes influencing all organ systems
In order to analyze the relationship between hypothyroidisms and cardiac function in old rats, we induced a state of hypothyroidism in the animals by surgically resecting their thyroid and parathyroid glands, and measuring the serum TSH, T3, T4 and free ionic calcium levels
Summary
Thyroid hormones are essential for the development of several organs and tissues and to maintenance of quality of life. They produce a general increase in carbohydrate, lipid and protein metabolism and are indirectly involved in transcriptional regulation of genes influencing all organ systems. Triiodothyronine (T3) and thyroxine (T4) are important thyroid hormones in regulating cardiovascular and hemodynamic function. The cardiovascular system responds to small changes in thyroid hormones levels through alterations of the vascular response and endothelial function. Hypothyroidism causes cardiomyocyte atrophy and decreased ventricular pressure and contractility [4,5]. The hemodynamic changes that characterize hypothyroidism include decrease in cardiac contractility, cardiac output, heart rate (HR) and ventricular function in general. The relation between thyroid hormones and aging on the cardiovascular function is controversial [2,6]
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