Background: Thyroid hormone excess is accompanied by many cardiovascular symptoms. We hypothesised that mechanical properties of the large arteries are also involved in hyperthyroidism-induced cardiovascular changes and set out to investigate this further.
Methods: We compared 2 groups: one composed of hospitalized patients with newly diagnosed, non-treated Graves' disease (Graves' group) and the other (control group) composed of healthy persons or patients with euthyroid goiter (n=25 and n=23, respectively). We determined values of cross-sectional compliance (CC(100)), distensibility (DC(100)) and stiffness coefficients (alpha(100)) estimated for blood pressure P(n)=100 mmHg by measuring the blood pressure with the oscillometric method and measuring differences in the diameter of the common carotid artery with ultrasonographic vascular echo Doppler system.
Results: We found no differences in CC(100) (10.6 vs 10.3 10(-4)m(2)/Mpa), DC(100) (29.7 vs 29.6 1/Mpa) or alpha(100) (2.67 vs 2.72) between the 2 groups. However, there were strong correlations between all stiffness parameters and plasma thyroid hormone concentrations in the Graves' group (r(s)=0.4698, p<0.001 for DC(100), r(s)=0.4342, p<0.003 for CC(100), r(s)=-0.4698, p<0.001 for alpha(100) and fT3, respectively). This relationships remained significant after statistical corrections for age and lipid levels (r(p)=0.22, p<0.03 for DC(100) and fT3 or r(p)=-0.457, p<0.02 for alpha(100) and fT3, respectively).
Conclusions: These results indicate that in the Graves' group the stiffness of the common carotid artery might be affected by the thyroid hormone level and the lower the level, the more severe the activity of the hyperthyroidism reflected by the plasma concentration of fT3 or fT4.