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अमूर्त

The Effects of Total Thyroidectomy on Cardiac Function in Old Rats using Echocardiographic Measures

Julio Cesar Francisco, Ricardo Correa Cunha, Marco André Cardoso, Rossana Baggio Simeoni, Luiz Cesar Guarita-Souza, Nelson Itiro Miyague and Katherine Athayde Teixeira de Carvalho

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.