Evaluation of acute physiological and molecular alterations in surgically developed hypothyroid Wistar rats

Objectives: To explore the general physiological and molecular changes occurring as a result of acute hypothyroidism. Materials and Methods: Hypothyroidism was developed by thyroidectomy in wistar rats. After surgery, animals were observed for 14 days in order to determine changes in body weight, feed consumption, rectal temperature, heart rate, and blood pressure, clinical pathological and hormonal alteration. In addition, relative changes in weight, histopathology and MHC – a and b gene expression of heart was also evaluated. Results: Thyroidectomised rats showed lethargy, piloerection and decreased locomotors activity. Day dependent significantly decreased body weight and feed consumption were seen in hypothyroid rats. Rectal temperature was significantly reduced at day 7 and 14 after surgery. Heart rate and blood pressure were significantly decreased at day 14 in thyroidectomized rats in comparison with euthyroid rats. Haematological parameters shown high WBC count. Serum LDL and phosphorous levels were high where as triglycerides; total protein, creatinine kinase and globulin were low. Heart weight was significantly high. Histopathology of heart tissue showed myocardial segmental degeneration. Downregulation of MHC – a and upregulation of MHC – b were seen in hypothyroid rats in comparison with euthyroid rats. Conclusion: This finding suggests that deficiency of thyroid hormone (TH) in hypothyroidism is associated to a cardiac dysfunction and acute changes in body homoeostasis as result of sudden arrest of thyroid hormone.