October 24, 2016
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Thyroid hormones associated with cardiometabolic risk factors in adolescents

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Triiodothyronine, thyroxine and thyroid-stimulating hormone levels were correlated with several cardiometabolic risk factors among adolescents with normal thyroid function, data from a recently published study found.

“Increased TSH levels, even within the ‘euthyroid’ range, have been associated with cardiometabolic risk factors, such as BMI, lipid status and blood pressure, in adults, with moderate evidence linking high-normal TSH levels with increased likelihood of metabolic syndrome and spontaneous pregnancy loss,” Trang N. Le, MD, of the division of endocrinology and metabolism, department of internal medicine and division of pediatric endocrinology and metabolism at the Children’s Hospital of Richmond and Virginia Commonwealth University, and colleagues wrote. “The relations between TSH, free T4 and free T3 and cardiometabolic risk factors are incompletely characterized in children and adolescents.”

Le and colleagues examined data from the United States National Health and Nutrition Examination Survey between 2007 and 2010, analyzing thyroid hormones, TSH levels, BMI, blood pressure, lipids and glucose metabolism among patients aged 12 to 18 years (n = 1,167). Mean age was 15 years, and 53% of patients were male. 

Mean TSH was 1.60 µIU/mL. Girls had slightly lower systolic blood pressure, TSH and fasting glucose levels than boys, but higher HDL levels. There was no difference between sexes in BMI, BMI z-score, diastolic blood pressure, LDL, triglycerides, apolipoprotein B or glucose metabolism. Mean free T4 was the same in girls and boys, but girls had significantly lower mean free T3 and total T3 levels, as well as a lower free T3:free T4 ratio (P < .0001). Adolescents with obesity had a higher mean TSH level than those with healthy weight or overweight (P = .0009), as well as a significantly higher free T3:free T4 ratio (P < .0001), but significantly lower mean free T4 levels (P = .0019). Researchers reported that black and Mexican American adolescents had the highest BMI z-scores (0.78 and 0.76). Le and colleagues found no racial or ethnic differences in TSH levels or free T3:free T4 ratio.

The findings were consistent with data from a similar survey of adults, the researchers noted.

“In conclusion, the present observations in a large unselected population of U.S. adolescents demonstrate that thyroid hormone homeostasis and indexes of peripheral metabolism of thyroid hormone have an important predictive role in cardiometabolic risk determination,” Le and colleagues wrote. “Future longitudinal studies would provide a better assessment of whether these relations persist into adulthood, or if the subtle differences in thyroid hormone levels may be indicators of a cohort of adolescents who may benefit from earlier and more intensive interventions aimed at improving lifetime cardiometabolic risk.” – by Andy Polhamus

 

Disclosure: Le reports no relevant financial disclosures. Please see the full study for a complete list of all other authors’ relevant financial disclosures.