Relationship of TSH levels with cardiometabolic risk factors in US youth aged 12-18 years and population-based reference percentiles for thyroid function tests.

ContextThyroid hormones play an important role in the metabolic homeostasis of the body and have been associated with cardiometabolic risk. ObjectiveTo examine the association of cardiometabolic risk factors (CMRF) with TSH levels in youth at population level in the US. Design & SettingCross-sectional study of youth aged 12-18 years without known thyroid abnormalities from National Health and Nutrition Examination Survey 1999-2012. Subclinical hypothyroidism (SH) was defined as TSH levels 4.5-10 mIU/L. Assessed CMRF included abdominal obesity (waist circumference > 90thpercentile), hypertriglyceridemia (TG [&ge;] 130 mg/dL), low HDL cholesterol (HDL-C < 40 mg/dL), elevated blood pressure (SBP and DBP [&ge;] 90thpercentile), hyperglycemia (FBG [&ge;] 100 mg/dL, or known diabetes), insulin resistance (HOMA-IR > 3.16) and elevated alanine transferase (ALT [&ge;]50 U/L for boys and [&ge;]44 U/L for girls). Age and sex-specific percentiles for thyroid parameters were calculated for youth with normal weight. ResultsIn this cohort of youth (51.3% male), 31.2% had overweight/obesity. The prevalence of SH was 2.0 % (95% CI 1.2-3.1). The median TSH levels were higher in youth with overweight/obesity (p<.001). Adjusting for age, sex, race/ethnicity and level of obesity, youth with TSH in the 4th quantile had higher odds of abdominal obesity (OR 2.53 [1.43-4.46], p = .002), higher HOMA-IR (OR 2.82 [1.42-5.57], p=.003) and [&ge;] 2 CMRF (OR 2.20 [1.23-3.95], p=.009). ConclusionsThe prevalence of SH is low in US youth. The higher odds of insulin resistance and CMRF in youth with TSH levels > 75th percentile requires further study.