Increased levels of C-reactive protein in hypothyroid patients and its correlation with arterial stiffness in the common carotid artery

Abstract

Objective Hypothyroidism is associated with increased morbidity from cardiovascular disease. The arterial stiffness index beta (stiffness β) in the common carotid artery (CCA), which is a parameter of arterial stiffening, is known to increase in hypothyroid patients, while normalization of thyroid function for 1 year by levothyroxine (L-T 4) replacement therapy significantly decreases CCA stiffness β. Since serum C-reactive protein (CRP) has recently emerged as an independent factor for cardiovascular risk, the present study was designed to examine whether hypothyroidism causes an increase in CRP and whether the serum CRP level is correlated with CCA stiffness β in hypothyroid patients. Patients and methods Serum CRP levels and CCA stiffness β were determined in 46 patients with hypothyroidism and in 46 age- and sex-matched normal control subjects. Thirty-five patients were further monitored for change in CCA stiffness β during 1 year in the euthyroid state induced by L-T 4 therapy. Results Baseline CRP and CCA stiffness β were both significantly higher in hypothyroid patients than in normal controls [1064.6 ± 224.3 vs. 602.1 ± 43.3 ng/ml (mean ± SE), p < 0.0001; and 9.25 ± 0.84 vs. 8.21 ± 0.85, p < 0.05, respectively]. Baseline CRP was significantly correlated in a positive manner with baseline values of CCA stiffness β ( r = 0.683, p < 0.0001). In multivariate analysis, baseline CCA stiffness β was significantly associated with baseline levels of serum CRP ( r = 0.740, p < 0.0001). During 1 year of L-T 4 replacement therapy, significant decrease in stiffness β (from 9.25 ± 0.84 to 8.57 ± 0.58, p < 0.0001) to the normal levels was found. Moreover, the change in CCA stiffness β during L-T 4 replacement therapy was significantly and independently associated in a negative fashion with baseline levels of serum CRP ( r = −0.696, p = 0.0002). Conclusions This study suggests that increased serum CRP might have an important independent role in increased arterial stiffening and the measurement of serum CRP is a useful predictor for the degree of improvement of arterial stiffening in hypothyroid patients.