Low total and free triiodothyronine levels are associated with insulin resistance in non-diabetic individuals

Chih-Yuan Wang,Tien-Chun Chang,Shyang-Rong Shih,Tse-Ya Yu,Kuo-Chin Huang

doi:10.1038/s41598-018-29087-1

Abstract

This study examined associations of thyroid hormone levels and insulin resistance (IR) in non-diabetic individuals. Using a cross-sectional design, 2007–2008 data from the National Health and Nutrition Examination Survey (NHANES) were analyzed. NHANES participants ≥20 years of age with complete data of interest were included. The homeostatic model assessment (HOMA) was used to quantify IR, and treated as a continuous variable. Self-reported diabetes or a fasting glucose ≥7 mmol/L were used as criteria to exclude diabetic subjects. Race, liver function, obesity, hypertension, dyslipidemia, smoking, physical activity, vigorous recreational activity, 2-hour glucose, hemoglobin A1C (HbA1C), high-density lipoprotein, triglyceride, vitamin D and C-reactive protein were covariates significantly associated with HOMA-IR. A total of 1,560 non-diabetic subjects were included in the analysis. When adjusted for all factors significant in the univariate analysis (race, liver function, obesity, hypertension, dyslipidemia, smoking, physical activity, vigorous recreational activity, 2-hour glucose, HbA1C, high-density lipoprotein, triglyceride, vitamin D, and CRP) low total triiodothyronine (TT3) and low free T3 (FT3) were significantly associated with decreased HOMA-IR (adjusted coefficient = −0.486, 95% confidence interval [CI]: −0.936, −0.036; adjusted coefficient = −1.151, 95% CI: −1.952, −0.350, respectively). Insulin resistance is associated with low thyroid hormone levels in non-diabetic individuals.

Highlights

Insulin resistance (IR) is defined as a glucose homeostasis disorder involving a decreased sensitivity of muscles, adipose tissue, liver, and other body tissues to insulin, and insulin resistance (IR) is a hallmark feature of type 2 DM1
A longitudinal study of obese children found that IR and thyroid stimulating hormone (TSH) were positively correlated, independent of body status, and a decrease in TSH levels was independently associated with decreases in homeostatic model assessment (HOMA)-IR12
When adjusted for all factors found to be significant in the univariate analysis low TT3 and low free T3 (FT3) were significantly associated with decreased HOMA-IR (Table 2)

Summary

Introduction

Insulin resistance (IR) is defined as a glucose homeostasis disorder involving a decreased sensitivity of muscles, adipose tissue, liver, and other body tissues to insulin, and IR is a hallmark feature of type 2 DM1. Thyroid disease is much more common in patients with DM than in the general population, suggesting a possibly relationship between thyroid hormone levels and insulin sensitivity[3]. Thyroid hormones exert both insulin agonistic and antagonistic actions in different organs, and studies have indicated thyroid hormones play a role in the development of IR through complex, intertwined mechanisms of biochemical, genetic, and secretory malfunctions[4,5,6,7,8]. Another study of euthyroid adolescents with risk factors for the development of diabetes reported a correlation between fasting insulin, IR, and serum thyroid hormone www.nature.com/scientificreports/. The purpose of this study was to use a large population-based database to examine the associations of thyroid hormone levels and IR in non-diabetic individuals

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Conclusion