[Thyroid hormones and their action on the myocardium]

Thyroid hormones are closely related to cardiac structure and function. We have been studying their effects for over 15 years in various experimental models:--Daily triidothyronin (T3) administration to rats for 14 days improves the ability of the isolated heart to tolerate ischemia, without abolishing the capacity for ischemic preconditioning (IP).--When hypothyroidism is induced in rats by administering propylthiouracil for 21 days, the isolated heart is markedly more tolerant of 30 min of global ischemia but can no longer undergo IP.--After myocardial infarction induced in rats by left coronary artery ligation, the post--infarct heart is protected against global ischemia but its contractility is reduced. T3 administration for 2 and 13 weeks significantly improves contractility and reduces both remodeling and the sphericity index.--TNF exposure delays cultured neonatal rat myocyte elongation (maturation), and this effect is prevented by concomitant T3 administration.--Thus, thyroid hormones offer valuable insights into cardiac structure and function and may have therapeutic potential in patients with cardiovascular disease.