Flow-mediated, endothelium-dependent vasodilatation is impaired in subjects with hypothyroidism, borderline hypothyroidism, and high-normal serum thyrotropin (TSH) values

Patients with hypothyroidism are considered to have an increased risk of developing atherosclerosis; because endothelial dysfunction is an early sign of atherosclerosis, we investigated whether endothelial dysfunction is present in patients with hypothyroidism. Thirty-five subjects with various TSH levels were investigated by high-resolution ultrasound imaging of the brachial artery to assess endothelial and smooth muscle responses. Flow-mediated, endothelium-dependent vasodilatation was significantly higher in subjects with TSH 0.4-2 mu IU/mL (11.8+/-2.7%), compared with subjects with TSH 2.01-4 mu IU/mL (6.8+/-2.9%), 4.01-10 mu IU/mL (5.2+/-6.3%) and >10 mu IU/mL (4.0+/-4.4%); TSH levels correlated inversely to endothelium-dependent dilatation. Thus, flow-mediated vasodilatation, a marker of endothelial function, is impaired not only in patients with mild hypothyroidism but also in subjects with ''high-normal'' serum TSH levels tie, 2.01-4.0 mu IU/mL) that may be characterized as possibly abnormal.