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Doug Mann LPN, LNC

Cardiovascular Effects of Thyroid Hormones

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Cardiovascular effects of thyroid hormones

Below are 4 brief extracts from medical journal abstracts that address the effects of thyroid hormones on the cardiovascular system.
The Journal of Clinical Endocrinology & Metabolism
Volume 90, No. 11, pages 5985-5990; 2005
Aggregation of High-Normal Thyroid-stimulating Hormone in Hypertensive families
Olga Gumieniak, et al

Thyroid hormone has multiple effects on cardiovascular system, including modulation of vascular tone. Overt and subclinical hypothyroidism are associated with an increase in systemic vascular resistance and hypertension. Variation in serum thyroid hormone concentrations within the euthyroid range also influences cardiovascular health, including endothelium-dependent vasodilation and hypertension.
J. Hypertonie 2004; 8 (2): 17-20
Schilddruse und Herz (Thyroid function and the heart)
Abstract [Translated to English from German, full text available in German only]

The impact of thyroid function on the heart and on the peripheral circulation is well established. Hyperthyreosis [hyperthyroidism] is usually associated with peripheral vasodilation, an increase in cardiac output and a decrease in diastolic blood pressure, sometimes with systolic hypertension. In contrast, in patients with hypothyreosis [hypothyroidism]  -- with or without clinical symptoms -- peripheral resistance increases, favoring the development of diastolic arterial hypertension. In the left ventrical, diastolic relaxation may be prolonged. Both disorders, diastolic ventricular dysfunction and enhanced ventricular afterload, contribute to a reduction of cardiac output. In addition to lipid abnormalities and high peripheral catecholamine levels typical for hypothyreosis, these homodynamic abnormalities increase the coronary risk considerably. Accordingly, appropriate thyriod hormone substitution is essential for correction of the cardiac and circulatory disorders in patients with hypothyreosis. In case of frank diastolic hypertension, treatment with antihypertensive drugs should be performed in addition. As soon as euthyreosis [a euthyroid state] is achieved, anti-hypertensive drugs may be gradually tapered, but diastolic blood pressure levels should be kept well below 90 mmHg. 
American Family Physician; Sept.1, 2002; Richard Sadovsky
Thyroid hormone effect on hypertension, aortic stiffness
[Conclusions from a study of hypertensive, hypothyroid patients]
The authors conclude that hypothyroidism causes aortic stiffness and hypertension (usually diastolic). Thyroid hormone therapy decreases aortic stiffness, promoting decreased blood pressure in about 50 percent of these patients. Antihypertensive treatment further improves aortic elasticity and can decrease blood pressure among patients with hypertension and hypothyroidism whose blood pressure does not drop as thyroid function is normalized.
The Journal of Clinical Endocrinology and Metabolism; March 14, 2006; Vol 91, #6, 2126-2132
Subclinclinical Hypothyroidism, Arterial Stiffness, and Myocardial Reserve
P.J.D. Owen, et al 

[Conclusions of a six month observational study of 19 female SubClinical Hypothyroid (SCH) patients with raised TSH, normal free T4, and no cardiovascular disease, using pulse wave analysis and tissue Doppler dobutamine stress echocardiography]
Arterial stiffness was increased in SCH and improved with L-thyroxin, which may be beneficial, whereas myocardial functional reserve was similar to controls and remained unaltered after treatment.

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