Serum TSH level in healthy Koreans and the association of TSH with serum lipid concentration and metabolic syndrome.
OBJECTIVE
The proper treatment of subclinical hypothyroidism and the normal range of serum thyroid stimulating hormone (TSH) concentration are intensely debated. However, few reports have investigated TSH concentrations in Asian ethnic groups. Therefore, the present study was designed to define the TSH reference range in a Korean population and to investigate the metabolic significance of TSH concentration.


METHODS
We enrolled patients who underwent medical examination at the CHA Bundang Medical Center. Anthropometric data were evaluated, and serum TSH, free T4, and lipid profiles were assayed.


RESULTS
A total of 7,270 subjects were included. Mean TSH concentration of the study population was 1.82 ± 0.95 mU/L, and we observed a sex-related difference in TSH concentration (male, 1.67 ± 0.87 mU/L; female, 2.02 ± 1.01 mU/L; p < 0.01). When the 2.5 and 97.5 percentiles were calculated, 95% TSH reference limits were 0.52-4.29 mU/L. TSH concentration was higher in elderly subjects, during winter, in postmenopausal women, and in obese males. Moreover, TSH showed significantly positive correlations with serum total cholesterol, triglyceride, and low density lipoprotein cholesterol regardless of sex, age, season, obesity, or menopausal status (all p < 0.01). Finally, TSH concentration was positively related to the prevalence of metabolic syndrome.


CONCLUSIONS
We demonstrated the association between TSH concentration within the normal reference range and serum lipid levels. TSH concentration varies according to sex, age, season, and body mass index (only in males). Moreover, high normal TSH levels were significantly associated with an increased prevalence of metabolic syndrome, which may be of importance when evaluating subjects with high normal TSH concentration.
Divison of Endocrinology and Metabolism, Department of Internal Medicine, CHA University College of Medicine, Seongnam, Korea.
Yeo Kyung
YK
Lee
Jo Eun
JE
Kim
Hyun Ju
HJ
Oh
Kyung Sun
KS
Park
Soo Kyung
SK
Kim
Seok Won
SW
Park
Moon Jong
MJ
Kim
Yong Wook
YW
Cho
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D006801:Humans; D007723:Korea / Q000453:epidemiology; D008055:Lipids / Q000097:blood*; D008297:Male; D008593:Menopause; D024821:Metabolic Syndrome / Q000097:blood* / Q000453:epidemiology; D008875:Middle Aged; D018570:Risk Assessment; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*; D055815:Young Adult
D008055:Lipids; D013972:Thyrotropin