Thyroid Hormones , Subclinical Hypothyroidism and Its Importance in Cardiovascular Disease

Hypothyroidism is a common endocrine disease that is classically described as a low level of thyroxine (T4) and triiodothyronine (T3) and high plasma level of thyroid stimulating hormone and that affects between 5 to 8% of adult women and a lower percentage of men. Several cardiovascular manifestations are associated with chronic hypothyroidism including low cardiac index, decrease in intravascular volume, increase in systemic vascular resistance and hypertension. Determining when hypothyroidism leads to cardiac infarction is difficult because it can generate cardiovascular changes that overlap with it, such as decreased minute volume and inotropism, an increase in the diameter of cavities/parietal thickness, among others. Several potential cellular mechanisms are those that can lead to infarction in hypothyroidism, such as alteration of plasma lipids, accelerated atherosclerosis, stimulation of myocardial fibrosis, vasoconstriction, induction of a genetic program that resembles hypertrophic pathology and ventricles with thin and dilated walls. With this review it is intended to show the importance of the good functioning of the thyroid hormones and their association with the pathology of cardiovascular and metabolic diseases.