Background: Increased thyrotropin (TSH) levels and free triiodothyronine to free thyroxine (fT3:fT4) ratios, even within the euthyroid range, have been associated with cardiometabolic risk factors in adults but are less characterized in youth. This study sought to determine relations between TSH, thyroid hormones, and cardiometabolic risk factors in euthyroid adolescents.
Methods: Data were extracted from the United States National Health and Nutrition Examination Survey, 2007-2010, for univariate and multivariate analyses of TSH, thyroid hormones, body mass index (BMI), blood pressure, lipids, and glucose metabolism. Subjects aged 12-18 years, with normal TSH and antithyroid peroxidase antibody levels, and without a history of thyroid disease, diabetes, or treatment of hypertension/dyslipidemia (n = 1167) were included. TSH and thyroid hormones were assessed for impact on BMI Z-score, systolic blood pressure (SBP) diastolic blood pressure, total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, triglycerides, and glucose metabolism.
Results: Univariate analyses revealed positive linear relations between TSH and SBP, TC, fasting and two-hour glucose, and homeostasis model assessment of insulin resistance (HOMA-IR). The fT3:fT4 ratio negatively correlated with high-density lipoprotein cholesterol but positively with BMI Z-score, SBP, triglycerides, fasting and two-hour glucose, fasting insulin, and HOMA-IR. In multivariate analyses controlling for age, sex, race/ethnicity, and BMI Z-score, relations between TSH and both TC and fasting glucose remained significant, and the fT3:fT4 ratio was positively associated with fasting glucose and HOMA-IR.
Conclusions: In an unselected population of euthyroid U.S. adolescents, TSH and thyroid hormones correlate with multiple cardiometabolic risk factors, with age- and sex-independent effects on cholesterol and glucose metabolism.