Endocrinol Metab.  2016 Jun;31(2):311-319. 10.3803/EnM.2016.31.2.311.

Triiodothyronine Levels Are Independently Associated with Metabolic Syndrome in Euthyroid Middle-Aged Subjects

Affiliations
  • 1Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Seoul Hospital, Soonchunhyang University College of Medicine, Seoul, Korea.
  • 2Division of Endocrinology and Metabolism, Department of Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
  • 3Division of Endocrinology and Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. thyroid@skku.edu

Abstract

BACKGROUND
Recent studies have shown an association between thyroid hormone levels and metabolic syndrome (MetS) among euthyroid individuals; however, there have been some inconsistencies between studies. Here, we evaluated the relationship between thyroid hormone levels and MetS in euthyroid middle-aged subjects in a large cohort.
METHODS
A retrospective analysis of 13,496 euthyroid middle-aged subjects who participated in comprehensive health examinations was performed. Subjects were grouped according to thyroid stimulating hormone, total triiodothyronine (T3), total thyroxine (T4), and T3-to-T4 ratio quartile categories. We estimated the odds ratios (ORs) for MetS according to thyroid hormone quartiles using logistic regression models, adjusted for potential confounders.
RESULTS
Of the study patients, 12% (n=1,664) had MetS. A higher T3 level and T3-to-T4 ratio were associated with unfavourable metabolic profiles, such as higher body mass index, systolic and diastolic blood pressure, triglycerides, fasting glucose and glycated hemoglobin, and lower high density lipoprotein cholesterol levels. The proportion of participants with MetS increased across the T3 quartile categories (P for trend <0.001) and the T3-to-T4 ratio quartile categories (P for trend <0.001). The multi-variate-adjusted OR (95% confidence interval) for MetS in the highest T3 quartile group was 1.249 (1.020 to 1.529) compared to the lowest T3 quartile group, and that in the highest T3-to-T4 ratio quartile group was 1.458 (1.141 to 1.863) compared to the lowest T3-to-T4 ratio quartile group, even after adjustment for potential confounders.
CONCLUSION
Serum T3 levels and T3-to-T4 ratio are independently associated with MetS in euthyroid middle-aged subjects. Longitudinal studies are needed to define this association and its potential health implications.

Keyword

Thyroid hormones; Triiodothyronine; Metabolic syndrome

MeSH Terms

Blood Pressure
Body Mass Index
Cholesterol, HDL
Cohort Studies
Fasting
Glucose
Hemoglobin A, Glycosylated
Humans
Logistic Models
Longitudinal Studies
Metabolome
Odds Ratio
Retrospective Studies
Thyroid Gland
Thyroid Hormones
Thyrotropin
Thyroxine
Triglycerides
Triiodothyronine*
Cholesterol, HDL
Glucose
Thyroid Hormones
Thyrotropin
Thyroxine
Triglycerides
Triiodothyronine
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