Abstract
ObjectivesLow-normal thyroid function is associated with numerous metabolic risk factors including insulin resistance (IR). Triglyceride-glucose (TyG) index is a new surrogate marker of IR calculated by fasting triglyceride and glucose levels. Here, we investigated the association between thyroid function and TyG index in non-diabetic euthyroid adults.MethodsThis cross-sectional study was based on data from the Korean National Health and Nutritional Examination Survey 2015 including 1482 individuals (741 men and 741 women). Serum thyrotropin (TSH) and free thyroxine (fT4) levels were measured.ResultsAfter adjusting for confounders, there was an inverse relationship of TyG index with fT4 in men (β = –0.094, P = 0.009) and a positive relationship of TyG index with TSH in women (β = 0.078, P = 0.018). The lowest fT4 tertile in men (P = 0.001) and the highest TSH tertile in women (P = 0.010) exhibited increased TyG index after adjusting for confounders. The lowest fT4 tertile also showed increased homeostatic model assessment for IR (HOMA-IR) only in men (P = 0.006). Odds ratios (ORs) for the high TyG index, which was defined as the highest TyG quartile decreased in the highest and second highest tertile of fT4 in men (OR = 0.41 and OR = 0.45, respectively; P < 0.001) and increased in highest tertile of TSH in women (OR = 1.81, P = 0.031) after adjusting for confounders. The OR for high HOMA-IR defined as the highest HOMA-IR quartile was also lower in the highest and second highest fT4 tertiles in men (both OR = 0.47; P = 0.003).ConclusionsThis is the first study to suggest that TyG index is a good surrogate marker of IR in evaluating its relationship with thyroid function.
Highlights
Thyroid hormone has pleiotropic functions in the regulation of multiple metabolic processes, including glucose metabolism, lipid metabolism, and energy expenditure [1]
The Odds ratios (ORs) for high HOMA-insulin resistance (IR) defined as the highest homeostatic model assessment of IR (HOMA-IR) quartile was lower in the highest and second highest fT4 tertiles in men
This is the first study to suggest that TyG index is a good surrogate marker of IR in evaluating its relationship with thyroid function
Summary
Thyroid hormone has pleiotropic functions in the regulation of multiple metabolic processes, including glucose metabolism, lipid metabolism, and energy expenditure [1]. Low-normal thyroid function, defined as high thyrotropin (TSH) and/or low free thyroxine (fT4) levels within the normal reference range, as well as subclinical and overt hypothyroidism, have been reported to be associated with metabolic syndrome [4,5,6,7,8,9,10,11,12]. The traditional use of HOMA-IR as a representative surrogate marker for IR is limited because fasting insulin levels are not frequently measured in real-world clinical settings [13]. To overcome this limitation, a new indicator for IR has been adopted recently: the triglyceride-glucose (TyG) index, which is calculated based on fasting triglyceride and glucose levels [14]. The association between thyroid function and the TyG index has not been studied to date
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