Thyroid Disease and the Heart

In the citing paper

“At the cardiac level, stimulation of the β-type thyroid-hormone receptors determines an up-regulation of the calcium-dependent ATPase pumps of the endoplasmic reticulum and a reduced expression of the Phospholamban protein resulting in an inhibitory action.”

In the citing paper

“The positive chronotropic effect derives mainly from a direct action of T3 on the genes that regulate the activity of the cardiac-pacemaker.”

In the citing paper

“In the most severe forms, chronic and pericardial interstitial edema, associated with reduced myocardial contractility, can progress to cardiac tamponade [1, 3].”

In the citing paper

“Overt hypothyroidism causes an interstitial accumulation of glycosaminoglycans that attracts water from the endovascular compartment, reducing the effectiveness of medical therapy.”

In the citing paper

“At the peripheral level, the stimulation of the α-1 thyroid receptors, expressed by the endothelial and smooth muscle cells of the vessels, reduces peripheral resistance causing a decrease in diastolic pressure [1, 6].”

In the citing paper

“The presence of tachyarrhythmia associated with the previously described hemodynamic alterations is often the cause of high-rate heart failure, especially in patients with concomitant risk factors [1, 6].”

In the citing paper

“At the renal level, this effect leads to a reduced perfusion with consequent activation of the renin–angiotensin–aldosterone system (to which a direct effect of T3 via thyroid β-1 receptors probably also contributes) with a sodium-retentive action and an increase in circulating volume [1, 6].”

In the citing paper

“Although a role of cathecolaminergic stimulation has been hypothesized, this seems unlikely.”

In the citing paper

“The presence of hypothyroidism also involves a reduction in the activity of the myocardial pacemaker and a lengthening of the QT intervals which can lead to the appearance of advanced atrio-ventricular blocks or torsades-de-pointes resulting in ventricular tachycardia [1, 3].”

In the citing paper

“thyrotoxicosis determines an imbalance of coagulative homeostasis towards a state of hypercoagulability and reduced fibrinolysis characterized by an increase in the circulating levels of factor VIII, IX, fibrinogen and Von Willebrand factor [1, 6]”

In the citing paper

“Indeed, T3 induces an increase in the expression of β1-adrenergic receptors on myocardiocytes, increasing myocardial sensitivity to the action of catecholamines, as it simultaneously inhibits the cardiac expression of the catalytic isoforms of adenylate–cyclase, keeping the endocellular response unchanged [1, 6].”

In the citing paper

“Echocardiographic studies have shown that overt hypothyroidism is often associated with early diastolic dysfunction which, together with the frequent occurrence of diastolic hypertension and/or other risk factors in these patients, can lead to difficult-to-treat heart failure [1, 3].”

In the citing paper

“Conversely, only 5% of subjects with thyrotoxicosis under the age of 60 have AF [1, 6].”

In the citing paper

“Patients with overt hyperthyroidism, at a rate ranging from 10 to 25%, experience atrial fibrillation (AF) with even higher percentages in males over 60 years of age and in those with higher free T4 (FT4) values.”

In the citing paper

“The thyroid hormone is one of the key regulators of cardiac function and cardiovascular hemodynamics; therefore, inadequate thyroid hormone levels impair the relaxation of vascular smooth muscle cells and decrease cardiac contractility by regulating calcium uptake and the expression of several contractile proteins in cardiomyocytes.37,38”

In the citing paper

“Low thyroid hormone levels also increase systemic vascular resistance and induce endothelial dysfunction by reducing nitric oxide availability.37,38,39”

In the citing paper

“excess increases cardiac output by affecting stroke volume and heart rate(6,71).”

In the citing paper

“Patients with severe hyperthyroidism may have coronary vasospasm leading to chest pain at rest or myocardial ischemia(6,70,71,79).”

In the citing paper

“Life-threatening thyrotoxicosis or thyroid storm is a rare disorder characterized by multisystem involvement and mortality rates in the range of 8%-25% in modern series (25,72,226,227).”