Evaluation of Endothelial Function in Subclinical Hypothyroidism and Subclinical Hyperthyroidism

Abstract

Subclinical hypothyroidism and subclinical hyperthyroidism are two frequently occurring conditions for which exact therapeutic approaches have not yet been established. The aim of this study was to compare the endothelial function and carotid artery intimae-media thickness (IMT) of these two groups of patients to euthyroid subjects and to assess the effects of these conditions on endothelial function. Study groups comprised of 25 subclinical hypothyroid patients (mean age, 32.28 +/- 9.67 years), 13 subclinical hyperthyroid patients (mean age, 35.69 +/- 9.67 years), and 23 euthyroid subjects (mean age, 35.87 +/- 7.93 years). They were evaluated for flow-mediated dilatation (FMD), and carotid artery IMT. The groups were matched strictly for atherosclerotic risk factors. The subclinical hypothyroid group was found to have significantly lower FMD values. No significant differences were observed between the groups with respect to other vascular parameters. The only discriminative factor between the groups was the state of their thyroid function. Therefore, subclinical hypothyroidism may have adverse effects on endothelial function independent from other well-known atherosclerotic risk factors.

Consenso brasileiro para a abordagem clínica e tratamento do hipotireoidismo subclínico em adultos: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

“…Lekakis and cols. (80) were the first to describe a negative relationship between SCH and endothelium--dependent vasodilation, measuring the brachial artery flow-mediated dilation that was subsequently confirmed by other studies (81,82). In a randomized double-blind crossover study, Razvi and cols.…”

Association between subclinical hypothyroidism and severe diabetic retinopathy in Korean patients with type 2 diabetes

“…Furthermore, thyroid dysfunction may amplify cardiovascular disease risk in diabetic patients through interrelationships with dyslipidemia, insulin resistance, and vascular endothelial dysfunction [27]. SCH has been associated with endothelial dysfunction [3], atherosclerosis, and ischemic heart disease [4][5][6] in non-diabetic subjects. However, few studies have reported the association of SCH with cardiovascular disease in type 2 diabetic patients [7].…”

“…Diabetic retinopathy was classified according to the following grades [9]: (1) no diabetic retinal damage, (2) mild non-proliferative diabetic retinopathy (NPDR), (3) moderate NPDR, (4) severe NPDR, and (5) proliferative diabetic retinopathy (PDR). Retinopathy more severe than moderate NPDR (severe NPDR and PDR) was defined as severe diabetic retinopathy.…”

Free Triiodothyronine Concentrations are Inversely Associated with Elevated Carotid Intima-Media Thickness in Middle-Aged and Elderly Chinese Population

“…Overt hypothyroidism is associated with abnormal lipid metabolism and impaired endothelial function as well as increased risk of atherosclerosis and ischemic heart disease 3,4) . Mildly impaired thyroid function has also been shown to be associated with dyslipidemia 5,6) , enhanced lowgrade inflammation 6) , and endothelial function 7) , which were intermediary cardiovascular outcome variables.…”