Diabetes Metab J.  2019 Dec;43(6):867-878. 10.4093/dmj.2018.0130.

The Relationship between Thyroid Function and Different Obesity Phenotypes in Korean Euthyroid Adults

Affiliations
  • 1Division of Endocrinology and Metabolism, Department of Internal Medicine, Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea. pons71@hanmail.net
  • 2ARO, Clinical Trial Center, Pusan National University Hospital, Busan, Korea.
  • 3Kim Yong Ki Internal Medicine Clinic, Busan, Korea.

Abstract

BACKGROUND
Thyroid disease and metabolic syndrome are both associated with cardiovascular disease. The aim of this study was to investigate the correlation between thyroid hormones and obesity sub-phenotypes using nationwide data from Korea, a country known to be iodine replete.
METHODS
This study was based on data obtained from the sixth Korea National Health and Nutrition Examination Survey, administered from 2013 to 2015. A total of 13,873 participants aged ≥19 years were included, and classified into four groups: metabolically healthy non-obesity (MHNO), metabolically healthy obesity (MHO), metabolically unhealthy non-obesity (MUNO), and metabolically unhealthy obesity (MUO) by body fat on the basis of body mass index and metabolic health.
RESULTS
At baseline, serum free thyroxine (fT4) values were significantly higher in the MHNO phenotype (MHNO, 1.27±0.01 ng/dL; MHO, 1.25±0.01 ng/dL; MUNO, 1.24±0.01 ng/dL; MUO, 1.24±0.01 ng/dL, P<0.001) in total study population. However, this significant association no longer remained after adjustment for age, urine iodine concentration, and smoking (P=0.085). After adjustment for confounders, statistically significant association was observed between lower thyroid stimulating hormone (TSH) and MHNO phenotype (P=0.044). In men participants (not women), higher fT4 values were significantly associated with MHNO phenotype (P<0.001). However, no significant association was observed between thyroid function (TSH or fT4) and obesity phenotypes in groups classified by age (cutoff age of 55 years).
CONCLUSION
Although there was a difference by age and sex, we found that the decrease of TSH and the increase of fT4 values were associated with MHNO.

Keyword

Metabolic syndrome; Obesity; Phenotype; Sex; Thyroid hormones

MeSH Terms

Adipose Tissue
Adult*
Body Mass Index
Cardiovascular Diseases
Humans
Iodine
Korea
Male
Nutrition Surveys
Obesity*
Obesity, Metabolically Benign
Phenotype*
Smoke
Smoking
Thyroid Diseases
Thyroid Gland*
Thyroid Hormones
Thyrotropin
Thyroxine
Iodine
Smoke
Thyroid Hormones
Thyrotropin
Thyroxine
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