Relationship of Thyroid Function with Metabolic Parameters in Euthyroid Adults

Abstract

Objective: Thyroid hormones have a significant effect on carbohydrate, lipid metabolism disorders, and insulin resistance (HOMA-IR) development. Vitamin D (25(OH)D) has been shown also can affect not only the musculoskeletal system, but also almost all tissues in the body, including the thyroid in recent years. In the study, we aim of this study is to investigate the relationship between the levels of thyroid-stimulating hormone (TSH) within the reference range and metabolic parameters in adults. Methods: 561 adult outpatients were divided into 2 groups low normal range (0.27-2.5 mIU/mL) and high normal range (2.5-4.2 mIU/mL) according to TSH, and HOMA-IR, 25(OH)D, and lipid levels were compared. Results: A statistically significant positive correlation was found between TSH and HOMA-IR in both the low normal range group (r = 0.123, p = 0.041) and the high normal range group (r = 0.196, p = 0.001). In the high normal range group, the relationship between TSH with vitamin D (r =-0.200, p =0.003), cholesterol (r =0.143, p =0.024), LDL cholesterol (r =0.154, p =0.018), non-HDL cholesterol (r = 0.134, p = 0.035) levels was statistically significant. Conclusion: Our study shows that high normal TSH levels in euthyroid adults are related to higher insulin resistance and lower 25(OH)D levels, and this interaction is a major contributor to dyslipidemia. Thyroid hormones explain the metabolic disorder in the early stages of T2DM. Therefore, we believe that screening TSH levels and determining the optimal TSH target will be beneficial.