Large and medium sized artery abnormalities in untreated and treated hypothyroidism.

Abstract

Hypothyroidism is frequently accompanied by cardiac dysfunction, increased vascular resistance and a greater prevalence of hypertension. Whether this condition is also accompanied by alterations of large artery function and structure is not known, however. We investigated radial artery compliance and wall thickness as well as carotid artery compliance in 11 normotensive recently diagnosed and never treated hypothyroid patients. Fifteen euthyroid healthy age- and sex-matched subjects served as controls. No subject had evidence of large artery atherosclerotic lesions. Carotid artery diameter was evaluated continuously by a B-M mode device and carotid compliance obtained by the Reneman formula. Radial artery diameter and wall thickness were continuously acquired over the systodiastolic blood pressure range (beat-to-beat finger measurement) by an echo-tracking device, and compliance (Langewouters formula) was expressed as the integral of the area under the compliance/blood pressure curve normalized for pulse pressure. Patients with hypothyroidism showed greater radial wall thickness (+109%, P < 0.01) and compliance (+58%, P < 0.03) than controls. Carotid artery compliance was not different in the two groups. In 10 hypothyroid patients L- tiroxine therapy for 9.0 +/- 2.3 months did not change carotid artery function but markedly reduced radial artery wall thickness (-36%, P < 0.05) and compliance (-20%, P < 0.05). Hypothyroidism is associated with early arterial structural and functional alterations, which involve more muscular than elastic arteries. These alterations, however, are reversible by hormonal replacement therapy.