Cardiovascular Findings and Effects of Caffeine on Experimental Hypothyroidism

Background: Thyroid hormone deficiencies can disrupt organ functions, significantly impacting the cardiovascular system. Recently, the effects of thyroid hormones on the heart have garnered increased attention. However, most studies are conducted on humans using clinical data, while cellular-level and experimental studies remain limited. Objective: This study aimed to investigate the cardiovascular implications of hypothyroidism and evaluate the impact of caffeine on cardiac health in rats induced with hypothyroidism using propylthiouracil (PTU). Methods: The study involved 60 rats divided into six groups. Group 1 served as the untreated control. Group 2 received PTU for two months to induce hypothyroidism. Group 3 received PTU for one month, followed by caffeine for one month. Group 4 received caffeine for two months. Group 5 received both PTU and caffeine simultaneously for two months. Group 6 received PTU for one month, followed by one month under normal conditions. Results: During necropsy, normal thyroid glands were observed in Groups 1, 4, and 6, enlarged thyroids in Group 2, and smaller thyroids in Groups 3 and 5. Microscopic examination revealed varying thyroid histologies: Group 2 showed significant epithelial cell proliferation and absent colloid, while Groups 3, 5, and 6 had altered yet colloid-containing acini. Macroscopic inspection of hearts appeared normal across all groups. However, histopathological examination revealed significant hyperemia and microhemorrhages in Group 2, contrasting with normal findings in other groups. Immunohistochemical analysis indicated reduced cardiac troponin expression in Group 2, while other groups maintained prominent expression. Additionally, Group 2 displayed increased serum TSH levels and decreased T3 and T4 levels. Conclusion: The findings suggest that administering caffeine alongside or after PTU treatment in rats with experimentally induced hypothyroidism may ameliorate thyroid and cardiac irregularities. This study indicates caffeine's potential in mitigating the adverse effects of hypothyroidism on thyroid and heart health.