Guest guest Posted September 26, 2008 Report Share Posted September 26, 2008 Cardiac Effects of Thyroid Disease _http://heartdisease.about.com/od/lesscommonheartproblems/a/thyroidheart.htm_ (http://heartdisease.about.com/od/lesscommonheartproblems/a/thyroidheart.htm) The thyroid, a small gland located in the neck, is responsible for modulating many vital bodily functions. By producing just the right amount of thyroid hormone, it helps to regulate the body's metabolism (specifically, how much oxygen and energy the body uses,) as well as digestive function, muscle function, and the normal integrity of the skin. In fact, the thyroid has at least some effect on every organ in the body - including the heart. For people with almost any type of heart disease, disorders of the thyroid gland can worsen old cardiac symptoms or cause new ones, and can accelerate the underlying heart problem. Even worse, doctors frequently forget to think about the thyroid when cardiac symptoms are worsening, and if they don't think of it they will miss it. Often, it's the savvy patient who reminds the doctor that thyroid function ought to be checked. This is why it is useful for those with heart disease to know a little about the cardiac effects of thyroid disease. Disorders of the thyroid gland usually involve either the failure to produce enough thyroid hormone (hypothyroidism) or the production of too much (hyperthyroidism). Both types of thyroid disorders are common. Hypothyroidism and the heart Thyroid hormone is very important for normal cardiovascular function, so when not enough thyroid hormone is present neither the heart nor the blood vessels function normally. In hypothyroidism the heart muscle is weakened in both its contraction phase, and also its relaxation phase. This means that the heart cannot pump as vigorously as it should, and the amount of blood it ejects with each heart beat is reduced. In addition, because the heart muscle does not relax normally in between heart beats, a potentially serious condition called diastolic dysfunction may result. (Read about diastolic dysfunction here _http://heartdisease.about.com/od/livingwithheartfailure/a/diastolic_HF.htm_ (http://heartdisease.about.com/od/livingwithheartfailure/a/diastolic_HF.htm) ). Furthermore, hypothyroidism reduces the amount of nitric oxide in the lining of the blood vessels, causing them to stiffen. Cardiac symptoms of hypothyroidism Cardiac symptoms can be seen in anybody with hypothyroidism, but are especially likely in an individual who already has underlying heart disease. Common symptoms include: -- Shortness of breath on exertion and poor exercise tolerance. These symptoms, in most patients with hypothyroidism, are due to weakness in the skeletal muscles; but in patients with heart disease, the symptoms may be due to worsening heart failure. -- Slow heart rate (bradycardia.) The heart rate is modulated by thyroid hormone, so that in hypothyroidism the heart rate is typically 10 - 20 beats per minute slower than normal. Especially in patients who also have heart disease, however, hypothyroidism may worsen the tendency for premature beats (such as PVCs) and even tachycardias such as atrial fibrillation. -- Diastolic hypertension. One might think that, because a lack of thyroid hormone slows down the metabolism, people with hypothyroidism might suffer from low blood pressure. Usually the opposite is true - the arteries are stiffer in hypothyroidism, which causes the diastolic blood pressure to rise. -- Worsening of heart failure, or the new onset of heart failure. Hypothyroidism can make well-controlled heart failure worsen, and can produce heart failure for the first time in patients with relatively mild underlying heart disease. -- Edema (swelling.) Swelling can occur as a result of worsening heart failure. In addition, hypothyroidism itself can produce a type of edema called myxedema, caused by an accumulation of abnormal proteins and other molecules in the interstitial fluid (fluid external to the body's cells.) -- Worsening of coronary artery disease. While the reduction in thyroid hormone can actually make angina less frequent in patients who have angina, the increase in LDL cholesterol(bad cholesterol) and in C-reactive proteinseen with hypothyroidism can accelerate any underlying coronary artery disease. Hypothyroidism can be an extremely subtle condition, and often occurs without the typical, constellation of " textbook " symptoms doctors usually expect. It also occurs far more commonly than most doctors realize. So if you have anyof these symptoms and your doctor does not have a ready or convincing explanation for them, especially if you already have heart disease of any type, ask your doctor to measure thyroid hormone levels. Treatment of hypothyroidism The treatment of hypothyroidism can be a lot trickier than most doctors think, and there are many considerations patients ought to take into account. If you have hypothyroidism, I urge you to read about its treatment here _http://thyroid.about.com/_ (http://thyroid.about.com/) . Next page: Hyperthyroidism and the heart Cardiac Effects of Thyroid Disease - page 2 _http://heartdisease.about.com/od/lesscommonheartproblems/a/thyroidheart_2.htm _ (http://heartdisease.about.com/od/lesscommonheartproblems/a/thyroidheart_2.htm) Hyperthyroidism and the heart In hyperthyroidism, caused by the overproduction of thyroid hormone, the heart muscle is " whipped " like a horse, and for a person with heart disease it's like whipping a tired horse.. Thyroid hormone increases the force of contraction of, and the amount of oxygen demanded by, the heart muscle. It also increases the heart rate. For these reasons the work of the heart is greatly increased in hyperthyroidism. Hyperthyroidism increases the amount of nitric oxide in the lining of the blood vessels, causing them to dilate and become less stiff. Cardiac symptoms of hyperthyroidism Cardiac symptoms can be seen in anybody with hyperthyroidism, but can be particularly dangerous in people with underlying heart disease. Common symptoms include: -- Fast heart rate (tachycardia) and palpitationspalpitations. Occult hyperthyroidism is a common cause of an increased heart rate at rest and with mild exertion. Hyperthyroidism should always be ruled out with blood tests before making the diagnosis of Inappropriate Sinus Tachycardia. Especially in patients with underlying heart disease, hyperthyroidism can also produce a host of other arrhythmias such as PVCs, ventricular tachycardia, and especially atrial fibrillation. Indeed, it is important to rule out hyperthyroidism in a patient with atrial fibrillation and no clear underlying cause. -- Systolic hypertension. The forceful cardiac contraction increases the systolic blood pressure, though the increased relaxation in the blood vessels reduces the diastolic blood pressure. -- Shortness of breath on exertion. This can be due to the skeletal muscle weakness cause by hyperthyroidism, or to a worsening in heart failure. -- Heart failure. Hyperthyroidism itself can produce heart failure, but this condition is relatively rare. On the other hand, if pre-existing heart disease is present, worsening of heart failure with hyperthyroidism is common, and can be extremely difficult to treat. -- Worsening angina. Patients with coronary artery disease often experience a marked worsening in symptoms with hyperthyroidism. These can include an increase in chest pain (angina) or even a heart attack. As with hypothyroidism, hyperthyroidism can be present - and often is - without the classic, textbook symptoms. So patients with any of these cardiac symptoms that cannot otherwise be readily explained should have thyroid function measured. Furthermore, sometimes a " mild " hyperthyroidism can exist in which thyroid blood tests can be misinterpreted. In these cases thyroid hormone levels themselves are normal, but the level of thyroid stimulating hormone (TSH - a hormone excreted by the pituitary gland that regulates the thyroid gland) is low. A low TSH indicates hyperthyroidism, despite " normal " thyroid hormone levels. This pattern of thyroid blood tests especially ought to be sought in all patients displaying any of the above symptoms with no clear reason for them. Treating hyperthyroidism The " best " way of treating hyperthyroidism is controversial. In the U.S., most doctors immediately opt for ablating the overactive thyroid gland with radioactive iodine, then giving the patient thyroid hormone pills since the thyroid gland is no longer functional. This method is certainly " easiest " for the doctors, but often patients are left feeling chronically abnormal. Using drugs to partially suppress the thyroid gland - in the U. S., Tapazole or PTU - creates somewhat more of a long-term management issue for doctors, but may lead to ultimately happier patients. I urge patients contemplating therapy for hyperthyroidism to read Mary Shomon's book, Living Well With Hyperthyroidism, to get an objective viewpoint on ALL the options for therapy - especially before opting for an irreversible treatment like radioactive iodine therapy. Also, whether you have hyperthyroidism or hypothyroidism, please spend some time on Mary's thyroid website at About.com; the advice and support you'll find there are excellent. (http://www.papercut.biz/emailStripper.htm) (http://www.papercut.biz/emailStripper.htm) Quote Link to comment Share on other sites More sharing options...
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