36 This review highlights a growing body of evidence from animal studies and small-scale clinical trials suggesting that low cellular thyroid activity at the cardiac tissue level may adversely affect HF progression and that treatment may lead to improvement.
16,17 All cardiovascular alterations that have been reported in the presence of overt hypothyroidism have also been identified in scHypo, differing only in the extent of the alteration. 16 Clinical observations suggest a strong link between scHypo and poor outcome in patients with and without heart disease.
Reduced TH function in the heart could arise from 1 or more of the following mechanisms: (1) reduced T3 production and/or increased T3 degradation resulting from inhibition of D1 and D2 activity and/or increased activity of D3, (2) reduced TH uptake and/or increased T3 degradation in the cardiac tissue, (3) changes in TH membrane transporters.
Thyroid hormone also has extranuclear nongenomic effects on the cardiac myocyte and on the systemic vasculature. These effects of T3 can occur rapidly and do not involve TRE-mediated transcriptional events. 2426 These T3-mediated effects include changes in various membrane ion channels for sodium, potassium, and calcium, effects on actin polymerization, adenine nucleotide translocator 1 in.
An underactive thyroid - hypothyroidism - is estimated to affect as many as 10 to 20 percent of women in their lifetimes, and is more common in women than men. The symptoms of hypothyroidism include fatigue, depression, weight gain, hair loss, muscle and joint pains, and many other chronic and debilitating symptoms.
33 In patients with cardiac diseases, however, the prevalence of primary scHypo is similar to that reported in the general population. 18 scHypo is an independent risk factor for atherosclerosis and MI in women 24 and is associated with coronary artery disease and increased all-cause mortality in men.
In addition, we will discuss the new data that demonstrate the changes in thyroid hormone metabolism that arise from acute myocardial infarction and chronic congestive heart failure. The latter may have new and novel implications for the management of patients with congestive heart failure.
1 Low circulating levels of T3 in the absence of primary thyroid hypofunction have been found in 20 to 30 of patients with dilated cardiomyopathy. 18 Moreover, FT3 levels were inversely correlated to coronary artery disease, and low T3 levels conferred an adverse prognosis, even after adjustment for coronary risk factors in patients with coronary.
9,10 In patients with overt hypothyroidism, the lack of T4 feedback leads to TSH levels 20 mIU/L, whereas in milder or subclinical hypothyroidism the TSH levels are between 3 and 20 mIU/L with normal T4 and T3 levels.
The thyroid is a butterfly-shaped gland that wraps around the windpipe, behind the "Adam's Apple" area of the neck. The hormones produced by the gland are essential to stimulating metabolism, growth, and the body's capacity to process calories.
They were also twice as likely to have had heart attacks. This common condition, which frequently has no obvious symptoms for patients, and no observable symptoms for doctors, is a strong risk factor for both hardening of the arteries and heart attacks in older women.
A study in rats demonstrated that chronic hypothyroidism alone can eventually lead to HF. 2 Other studies suggest reduced cardiac tissue triiodothyronine (T3) levels after myocardial infarction (MI) or with development of hypertension by upregulating type 3 deiodinase (D3 which leads to deactivation of T3 and T4 (thyroxine).