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High Blood Pressure and Hypothyroidism

Also see:
Ray Peat, PhD on High Blood Pressure
Thyroid Status and Cardiovascular Disease
High Cholesterol and Metabolism
The Cholesterol and Thyroid Connection
The Truth about Low Cholesterol
Inflammatory TSH
“Normal” TSH: Marker for Increased Risk of Fatal Coronary Heart Disease
The Cholesterol and Thyroid Connection
High Blood Pressure and Hypothyroidism
A Cure for Heart Disease
Hypothyroidism and A Shift in Death Patterns

“The hypo-osmolar blood of hypothyroidism, increasing the excitability of vascular endothelium and smooth muscle, is probably a mechanism contributing to the high blood pressure of hypothyroidism. The swelling produced in vascular endothelium by hypo-osmotic plasma causes these cells to take up fats, contributing to the development of atherosclerosis. The generalized leakiness affects all cells (see “Leakiness” newsletter), and can contribute to reduced blood volume, and problems such as orthostatic hypotension. The swollen endothelium is stickier, and this is suspected to support the metastasis of cancer cells. Inflammation-related proteins, including CRP, are increased by the hypothyroid hyperhydration. The heart muscle itself can swell, leading to congestive heart failure.” -Ray Peat, PhD

Endocrinol Metab Clin North Am. 1994 Jun;23(2):379-86.
Hypertension in thyroid disorders.
Saito I, Saruta T.
Hypertension is more common in hypothyroidic patients than in euthyroid controls in older age groups. Treatment of the thyroid deficiency alone lowers blood pressure in most patients. Hemodynamically, cardiac output is reduced and total peripheral resistance is elevated. The latter probably is secondary to an increase of sympathetic nervous tone and a relative increase in alpha-adrenergic response. In hyperthyroidism, elevation of diastolic blood pressure is uncommon. Systolic hypertension is more common in younger age groups. Treatment of the hyperthyroidism alone lowers systolic blood pressure in most patients. An increase in cardiac output and a decrease in total peripheral resistance accompany the hyperthyroidism. Potentiation of catecholamine action by an excess of thyroid hormone has been invoked as an explanation, because thyroid hormone excess is accompanied by increased beta-adrenergic receptors in some tissue, including heart.

Thyroid. 2002 May;12(5):421-5.
Risk factors for cardiovascular disease in women with subclinical hypothyroidism.
Luboshitzky R, Aviv A, Herer P, Lavie L.
Overt hypothyroidism may result in accelerated atherosclerosis and coronary heart disease (CHD) presumably because of the associated hypertension, hypercholesterolemia, and hyperhomocysteinemia. As many as 10%-15% of older women have subclinical hypothyroidism (SH) and thyroid autoimmunity. Whether SH is associated with risk for CHD is controversial. We examined 57 women with SH and 34 healthy controls. SH was defined as an elevated thyrotropin (TSH) (>4.5 mU/L) and normal free thyroxine (FT(4)) level (8.7-22.6 nmol/L). None of the patients had been previously treated with thyroxine. In all participants we determined blood pressure, body mass index (BMI), and fasting TSH, FT(4), antibodies to thyroid peroxidase and thyroglobulin, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides, folic acid, vitamin B(12), creatinine, and total plasma homocysteine levels. The SH and control groups did not differ in their total homocysteine values. Mean diastolic blood pressure was increased in SH patients versus controls (82 vs. 75 mm Hg; p < 0.01). Mean values of TC, HDL-C, LDL-C, triglycerides, TC/HDL-C, and LDL-C/HDL-C were not different in patients with SH compared with controls. Individual analysis revealed that the percentage of patients with SH having hypertension (20%), hypertriglyceridemia (26.9%), elevated TC/HDL-C (11.5%), and LDL-C/HDL-C (4%) ratios were higher than the percentages in controls. Hyperhomocysteinemia (> or = 10.98 micromol/L) was observed in 29.4% of SH and was not significantly different from the percentage in controls (21.4%). No significant correlation between TSH and biochemical parameters was detected. We conclude that subclinical hypothyroidism in middle-aged women is associated with hypertension, hypertriglyceridemia, and elevated TC/HDL-C ratio. This may increase the risk of accelerated atherosclerosis and premature coronary artery disease in some patients.

The Journal of Clinical Endocrinology & Metabolism May 1, 2002 vol. 87 no. 5 1996-2000
The Role of Thyroid Hormone in Blood Pressure Homeostasis: Evidence from Short-Term Hypothyroidism in Humans
Enza Fommei and Giorgio Iervasi
Arterial hypertension is known to be frequently associated with thyroid dysfunction, with a particularly high prevalence in chronic hypothyroidism. However, to our knowledge no comprehensive study addressed causal mechanisms possibly involved in this association. We here report the physiological relationships between blood pressure and neuro-humoral modifications induced by acute hypothyroidism in normotensive subjects. Twelve normotensive patients with previous total thyroidectomy were studied. Ambulatory 24-h blood pressure monitoring was performed, and free T3, free T4, TSH, PRA, aldosterone, cortisol, adrenaline, and noradrenaline were assayed 6 wk after oral L-T4 withdrawal (phase 1) and 2 months after resumption of treatment (phase 2). During the hypothyroid state (TSH, 68.1 ± 27.7 μIU/ml; mean ± SD), daytime arterial systolic levels slightly, but significantly, increased (125.5 ± 9.7 vs. 120.4 ± 10.8 mm Hg; P < 0.05), and daytime diastolic levels (84.6 ± 7.9 vs. 76.4 ± 6.8 mm Hg; P < 0.001), noradrenaline (2954 ± 1578 vs. 1574 ± 962 pmol/liter; P < 0.001), and adrenaline (228.4 ± 160 vs. 111.3 ± 46.1 pmol/liter; P < 0.05) also increased. PRA remained unchanged (0.49 ± 0.37 vs. 0.35 ± 0.21 ng/ml·h; P = NS), whereas both aldosterone (310.3 ± 151 vs. 156.9 ± 67.5 pmol/liter; P < 0.005) and cortisol (409.2 ± 239 vs. 250.9 ± 113 pmol/liter; P < 0.02) significantly increased. By using univariate logistic regression daytime arterial diastolic values, noradrenaline and aldosterone were found to be significantly related to the hypothyroid state (P < 0.02, P < 0.036, and P < 0.024, respectively). In conclusion, our data show that thyroid hormones participate in the control of systemic arterial blood pressure homeostasis in normotensive subjects. The observed sympathetic and adrenal activation in hypothyroidism, which is reversible with thyroid hormone treatment, may also contribute to the development of arterial hypertension in human hypothyroidism.

Vojnosanit Pregl. 2007 Nov;64(11):749-52.
[Cardiovascular risk factors in patients with subclinical hypothyroidism].
[Article in Serbian]
Pesić M, Antić S, Kocić R, Radojković D, Radenković S.
BACKGROUND/AIMS:
Overt hypothyroidism is disease associated with accelerated arteriosclerosis and coronary heart disease. Whether subclinical hypothyroidism (SH) is associated with increased cardiovascular risk is contraversial. As SH is a high prevalence thyroid dysfunction, specially in older women, it is important to evaluate cardiovascular risk factors in these patients and that was the aim of this study.
METHODS:
We examined 30 patients with SH and 20 healthy controls. Subclinical hypothireoidism was defined as an elevated thyrotropin (TSH) (> 4.5 mU/L) and normal free thyroxine (FT4) level. In all the participants we determined body mass index (BMI), blood pressure, TSH, FT4, antibodies to thyroid peroxidase, antibodies to thyroglobulin, total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, triglicerides, total cholesterol/HDL cholesterol ratio and LDL/HDL cholesterol ratio.
RESULTS:
Mean BMI in patients with SH was significantly higher (p < 0.05), as well as diastolic blood pressure (p < 0.01) compared with the controls. Average levels of total cholesterol (5.40 +/- 0.62 vs 5.06 +/- 0.19 mmol/l, p < 0.01) and triglycerides (2.16 +/- 0.56 vs 1.89 +/- 0.24 mmol/l, p < 0.05) were also significantly higher in the group with SH. Individual analysis revealed that the percentage of patients with SH having borderline elevated total cholesterol (63.33%), hypertrigliceridemia (43.33%) and elevated total cholesterol/HDL cholesterol ratio (26.67%) were significantly higher than the percentage in the controls. No significant correlation between TSH and lipid parameters was detected.
CONCLUSION:
Subclinical hypothyroidism was associated with higher BMI, diastolic hypertension, higher total cholesterol and triglicerides levels and higher total cholesterol/HDL cholesterols ratio. This might increase the risk of accelerated arteriosclerosis in patients with SH.

Endocrine. 2004 Jun;24(1):1-13.
Hypothyroidism as a risk factor for cardiovascular disease.
Biondi B, Klein I.
The cardiovascular risk in patients with hypothyroidism is related to an increased risk of functional cardiovascular abnormalities and to an increased risk of atherosclerosis. The pattern of cardiovascular abnormalities is similar in subclinical and overt hypothyroidism, suggesting that a lesser degree of thyroid hormone deficiency may also affect the cardiovascular system. Hypothyroid patients, even those with subclinical hypothyroidism, have impaired endothelial function, normal/depressed systolic function, left ventricular diastolic dysfunction at rest, and systolic and diastolic dysfunction on effort, which may result in poor physical exercise capacity. There is also a tendency to increase diastolic blood pressure as a result of increased systemic vascular resistance. All these abnormalities regress with L-T4 replacement therapy. An increased risk for atherosclerosis is supported by autopsy and epidemiological studies in patients with thyroid hormone deficiency. The “traditional” risk factors are hypertension in conjunction with an atherogenic lipid profile; the latter is more often observed in patients with TSH >10 mU/L. More recently, C-reactive protein, homocysteine, increased arterial stiffness, endothelial dysfunction, and altered coagulation parameters have been recognized as risk factors for atherosclerosis in patients with thyroid hormone deficiency. This constellation of reversible cardiovascular abnormalities in patient with TSH levels <10 mU/L indicate that the benefits of treatment of mild thyroid failure with appropriate doses of L-thyroxine outweigh the risk.

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