Carotid artery intima-media thickness (CIMT) measurement has increasingly been used as a marker of atherosclerosis in many studies ( 10). Detecting and quantifying the existence of subclinical vascular disease, through vascular imaging, has been suggested as a means to enhance cardiovascular risk assessment ( 9). Assessment of endothelial dysfunction, being an early biomarker, is helpful in predicting cardiovascular risk and evaluating the outcome of treatment ( 8). So, the benefit from thyroid replacement therapy in SCH is still debatable.Įndothelial dysfunction is believed to be an early step in the development and progression of atherosclerosis. Some studies showed that there is an association, but others did not confirm that ( 5, 6, 7). Current controversy centers on whether subclinical hypothyroidism (SCH) is associated with atherosclerosis. Multiple mechanisms account for atherosclerosis in patients with hypothyroidism such as dyslipidemia, hypercoagulable state, increased arterial stiffness, obesity and endothelial dysfunction ( 1, 2, 3, 4). Hypothyroidism is associated with an increased risk for atherosclerotic cardiovascular disease owing to its metabolic and hemodynamic effects ( 1). Impairment of endothelial function is a contributing factor to the increased risk of atherosclerosis in both groups of patients. We concluded that CIMT is significantly higher in patients with overt and subclinical hypothyroidism compared with normal control subjects. CIMT negatively correlated with percent of change in blood flow following heat-mediated vasodilation in patients with overt and subclinical hypothyroidism ( P < 0.001 for both). The impairment was more significant in overt as compared with subclinical hypothyroidism ( P = 0.014). The percent of change in blood flow following heat-mediated vasodilation was significantly impaired in patients with overt and subclinical hypothyroidism as compared with the control group (328 ± 17 and 545 ± 406% respectively vs 898 ± 195%, P < 0.001 for both). CIMT was significantly higher in patients with overt and subclinical hypothyroidism as compared with the control group (0.7 ± 0.2 and 0.6 ± 0.2 mm respectively vs 0.45 ± 0.07 mm, P < 0.001 for both). Endothelial function was assessed by measuring the percent of change in blood flow following heat-mediated vasodilation using laser Doppler flowmetry. CIMT was measured using high-resolution color-coded Doppler ultrasonography. Forty, age- and sex-matched, subjects with normal thyroid functions were also included as a control group. We included 70 female patients with hypothyroidism in the study, 40 patients with overt and 30 patients with subclinical hypothyroidism. We assessed carotid intima-media thickness (CIMT), as a marker of atherosclerosis, and endothelial function in patients with hypothyroidism. Hypothyroidism is associated with increased risk of atherosclerosis.
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