To investigate the relationship between
thyroid function and
carotid intima-media thickness (CIMT) in a relatively large general population with euthyroid status we initially enrolled 1772 Japanese adults (421 men and 1351 women) who participated in a medical screening program for the general population over 40 years old. To evaluate only euthyroid subjects without vascular diseases and/or its major
risk factors, 1129 were excluded and 643 participants (175 men and 468 women) were included for further analysis. Simple and
multivariate linear regression analyses were performed to evaluate free
thyroxine (fT4) and
thyroid-stimulating hormone (TSH) levels and other existing parameters, including
carotid intima-media thickness. By
multivariate linear regression analysis adjusted for age and sex, free
thyroxine was significantly
correlated with
triglycerides (beta=0.07, p=0.015),
carotid intima-media thickness (beta=-0.091, p=0.049), and
thyroid-stimulating hormone (beta=-0.091, p=0.003).
Thyroid-stimulating hormone was significantly
correlated with
high-density lipoprotein cholesterol (HDL-C) (beta=-0.001, p=0.015), HbA(1c) (beta=0.038, p=0.045),
carotid intima-media thickness (beta=0.27, p=0.001), and free
thyroxine (beta=-0.15, p=0.003). When adjusted for
confounding factors, free
thyroxine was significantly
correlated only with
carotid intima-media thickness (beta=-0.13, p=0.043) and
thyroid-stimulating hormone was significantly
correlated with HDL-C (beta=-0.001, p<0.001), HbA(1c) (beta=0.04, p=0.021), and
carotid intima-media thickness (beta=0.29, p=0.001). We have demonstrated that
carotid intima-media thickness is independently associated with
thyroid function within the normal reference range, which suggests an increased
cardiovascular risk in subjects with low normal
thyroid function.
