Thyroid dysfunction and their relation to cardiovascular risk factors such as lipid profile, hsCRP, waist hip ratio in Korea

Jung, Chan Hee; Sung, Ki Chul; Shin, Hun Sub; Lhee, Hyun Young; Park, Seung Ha; Lee, Ho Chul; Rhee, Eun Jung; Lee, Won Young; Kim, Bum Soo; Kang, Jin Ho; Kim, Sun Woo; Lee, Man Ho; Park, Jung Ro; Kim, Sun Woo

Abstract

BACKGROUND: Thyroid abnormalities affect a considerable portion of the population. Overt hypothyroidism is associated with an elevated risk of cardiovascular disease and adverse changes in blood lipids. Subclinical hypothyroidism is also associated with an increase risk of cardiovascular disease. So we performed the study to investigate the prevalence of overt and subclinical thyroid disorders and their association between cardiovascular risk factors.
METHODS
This study was performed in 66,260 subjects (43,588 men, 22,672 women ; between 20~80 years of age, mean age 41.5+/-9.6). Serum free thyroxine (FT4), thyroid stimulating hormone (TSH), total cholesterol, low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) were measured with RIA using commercial kits. High sensitivity C-reactive protein (hsCRP) were measured with nephelometry.
RESULTS
The prevalence of overt thyrotoxicosis, subclinical thyrotoxicosis, overt hypothyroidism and subclinical hypothyroidism was 5/1000 (334 subjects), 6.4/1000 (426 subjects), 1.6/1000 (108 subjects), 6.4/1000 (375 subjects) population. Mean plasma total cholesterol and LDL-C were elevated in overt hypothyroidism than normal (202.1 mg/dL and 121.8 mg/dL versus 197.1 mg/dL and 120.1 mg/dL)(p < 0.05). Also in subclinical hypothyroidism, mean total cholesterol and LDL-C level were elevated compared to normal group (201.9 mg/dL and 123.7 mg/dL)(p=0.015, p=0.047). Waist-to-hip ratio (WHR) was lower in overt thyrotoxicosis and was higher in hypothyroidism.
CONCLUSION
The prevalence of thyroid dysfunction was not significantly different from those of other countries. It was also age dependent and higher in women but it was lower than expected. Patients with hypothyroidism exhibit higher levels of waist-to-hip ratio as index of obesity. Patients with subclinical hypothyroidism exhibited increased levels of the atherogenic parameters (Total cholesterol, LDL-C). Therefore screening and treatment for subclinical hypothyroidism may be warranted due to the adverse effects on lipid metabolism.