Abstract
Recent evidence indicates that low-normal thyroid function test results within the reference ranges may be related to increased cardiometabolic risk factors. The current study aimed to evaluate the relationship between thyroid function using thyroid-stimulating hormone (TSH) and free thyroxine (FT4) and cardiometabolic risk factors and the clustering of these risk factors (metabolic syndrome) in euthyroid children and adolescents. A total of 250 euthyroid children and adolescents aged 10–18 years were included using data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2015. In the unadjusted correlation analyses, TSH was positively correlated with glucose (r = 0.172, P = 0.006), hemoglobin A1c (HbA1c) (r = 0.149, P = 0.018), insulin (r = 0.144, P = 0.023), homeostatic model assessment for insulin resistance (HOMA-IR) (r = 0.163, P = 0.010), and triglyceride (TG) (r = 0.155, P = 0.014), whereas FT4 was negatively associated with the waist circumference (WC) standard deviation score (SDS) (r = −0.134, P = 0.035), body mass index (BMI) SDS (r = −0.126, P = 0.046), insulin (r = −0.219, P < 0.001), and HOMA-IR (r = −0.211, P < 0.001). In the multiple linear regression analysis, TSH was positively associated with glucose (β = 1.179, P = 0.021), HbA1c (β = 0.044, P = 0.039), and TG (β = 8.158, P = 0.041) after adjustment for possible confounders. FT4 was negatively associated with serum fasting insulin (β = −5.884, P = 0.017) and HOMA-IR (β = −1.364, P = 0.023) in the multiple linear regression analysis. Boys and girls with elevated glucose levels had a higher adjusted mean TSH level compared to those without elevated glucose levels after controlling for confounding factors in the analysis of covariance (2.16 mIU/L vs 3.88 mIU/L, P = 0.004). Our results suggest that higher TSH and/or lower FT4 levels, even within the reference ranges, may be related to increased cardiometabolic risk factors.
Highlights
Cardiovascular disease, which caused approximately 17.6 million deaths in 2016, is an important cause of morbidity and mortality worldwide[1]
Subclinical hypothyroidism (SCH) is defined as elevated serum thyroid-stimulating hormone (TSH) levels exceeding the limit of the reference range for age and sex, while the concentrations of serum free thyroxine (FT4) and free triiodothyroxine (FT3) remain within the reference ranges; SCH is more common than overt hypothyroidism, and the prevalence ranges from 4.6% to 9.0% in the adult population[9,12,13] and from 4.6% to 13.9% in children and adolescents[14,15]
TSH was significantly positively associated with glucose (β = 1.179, P = 0.021), hemoglobin A1c (HbA1c) (β = 0.044, P = 0.039) and TG (β = 8.158, P = 0.041), whereas TSH was positively but not significantly associated with homeostatic model assessment for insulin resistance (HOMA-IR) (β = 0.232, P = 0.060)
Summary
Cardiovascular disease, which caused approximately 17.6 million deaths in 2016, is an important cause of morbidity and mortality worldwide[1]. The disease is considered a major concern in adulthood, the age of onset has tended to be younger in recent decades[2]. Both risk factors related to cardiovascular disease, including abdominal obesity, increased blood pressure (BP), abnormal glucose regulation, decreased insulin sensitivity, dyslipidemia, and clustering of these risk factors, which is called metabolic syndrome (MetS), may begin early in life[3]. Emerging evidence indicates that higher TSH and/or lower free thyroid hormone levels within the reference ranges may be related to increased cardiometabolic risk in recent studies[18,19,20]. We evaluated the differences in levels of TSH and FT4 according to the presence of MetS and its components
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