Hemodynamic Changes After Levothyroxine Treatment in Subclinical Hypothyroidism

Abstract

In hypothyroidism, lack of thyroid hormones results in reduced cardiac function (cardiac output [CO]), and an increase of systemic vascular resistance (SVR). We speculated whether hemodynamic regulation in subjects with subclinical hypothyroidism (SH) (defined as mildly elevated thyrotropin [TSH] despite free thyroxine [T(4)] and triiodothyronine [T(3)] estimates within reference range) would benefit from levothyroxine (LT(4)) substitution. CO was measured by impedance cardiography, which is an observer independent method with high precision, and mean arterial pressure (MAP) by oscillometry. SVR was then calculated as MAP/CO. Measurements were performed before and after 60 degrees head-up tilting, and before and after LT(4) substitution. Plasma levels of catecholamines were also measured. In 16 otherwise healthy women with SH (ages 44-74 years; serum TSH in mean 17.1 mU/L (range, 6.8-27), and normal free T(4) and T(3) estimates) LT(4) treatment resulted in 6% reduction in supine MAP (p < 0.01), 14% increase in upright CO (p < 0.05), and 13%-20% decrease in SVR (supine and upright position, respectively) (p < 0.05). Plasma norepinephrine as well as epinephrine decreased during LT(4) treatment (p < 0.05). These changes were qualitatively similar but quantitatively less pronounced than in 15 women with overt hypothyroidism, also studied. Taking the two groups together (n = 31), pretreatment thyroid function (expressed as either TSH or free T(4) estimate) correlated to CO and SVR as well as the changes induced by LT(4) (p < 0.05), i.e., the lower the thyroid function the lower the CO and the higher the SVR, and the greater the response to LT(4). We conclude, that LT(4) treatment in SH results in changes in hemodynamic parameters of potentially beneficial character. SH and overt hypothyroidism should be regarded as a continuum, and our data favor earlier and more aggressive treatment of SH.

Cardiac function in borderline hypothyroidism: a study by pulsed wave tissue Doppler imaging

“…In this context, SH has been found to be associated with a deranged cardio-respiratory function, both at the level of anaerobic threshold and at peak exercise (23). Evidence suggesting systolic abnormalities in SH has recently been reported by other techniques such as ultrasonic myocardial textural analysis (24), impedance cardiography (25), and radionuclide ventriculography (26).…”

Monitorização ambulatorial da pressão arterial em pacientes normotensos com hipotireoidismo subclínico

“…Faber et al 24 found a decrease in systemic vascular resistance and in the mean arterial pressure with LT-4 replacement among 16 women (mean age 60 years) with SH and mean serum TSH = 17.1 mU/l 24 . Nagasaki et al 25 also demonstrated that SH patients exhibited increased DBP, in a group of elderly patients (65.2 ± 2.6 years old), with lower serum HDL cholesterol levels 25 .…”

Mild Thyroid Deficiency in the Elderly

“…Diastolic dysfunction both at rest and upon effort is the most consistent cardiac abnormality in patients with sHT, even in those with slightly elevated TSH levels (>6 mIU/L) (Arem et al, 1996;Biondi & Cooper, 2012;). Mild thyroid failure may also increase diastolic blood pressure as a result of increased systemic vascular resistances (Faber et al, 2002;Kahaly, 2000;Luboshitzky et al, 2002). Interestingly, restoration of euthyroidism by LT4 replacement is able to reduce systemic hypertension as well as improve left ventricular myocardial function (Brenta et al, 2003).…”