Hsps70 and 90 protect the heart of hyperthyroid rats via nitric oxide production and VEGF inhibition of apoptosis

•Treatment with carbimazole and levothyroxine altered thyroid function.•Altered thyroid state resulted induced oxidative signaling pathway.•Hyperthyroidism enhances nitric oxide production and inhibit apoptosis.•Hsp 70 and Hsp 90 production increased in hyperthyroidism.•Cardio protective role of Hsp 70 and Hsp 90 confirmed by reduced CK-MB and enhanced antioxidant system. . Changes occur in the heart's contractile and metabolic demands during altered thyroid states. The changes may be associated with alterations in the cellular signaling of vascular endothelial growth factors (VEGF) and expressions of heat shock proteins (Hsp). . This study examined the effects of thyroid dysfunction on VEGF, hsp70, and hsp 90 concentrations in the heart tissues of dysthyroid rats. . Wistar rats were allocated into control, hypothyroid (Carbimazole-treated), and hyperthyroid (Levothyroxine-treated) groups randomly (n=7). Thyroid function test, body weight changes, serum creatinine kinase (CK-MB), cardiac troponin I (cTnI) and troponin T (cTnT), NO, VEGF, Hsp70, and Hsp 90 were determined using standard methods. . There was a significant increase (P