An increased serum free triiodothyronine (FT3) level is an independent predictor for developing metabolic syndrome in patients who are euthyroid, according to a study published in Clinical Endocrinology.
The main function of the thyroid gland in the endocrine system is to regulate energy homeostasis and metabolism, but it is unclear whether thyroid hormones are useful for predicting the development of metabolic syndrome.
A few cross-sectional studies have examined the relationship between thyroid hormones or thyroid stimulating hormone and the onset of metabolic syndrome, while a small number of studies have looked only at the components of metabolic syndrome individually.
The current prospective cohort study (n=6119) was performed in Tianjin, China, and followed individuals without a history of metabolic syndrome for 1 to 3 years, with a median follow-up of 2 years. During the follow-up period, 1082 participants were diagnosed with metabolic syndrome, which was defined in accordance with the criteria of the 2009 American Heart Association Scientific Statements.
FT3, free thyroxine (FT4) and thyroid-stimulating hormone (TSH) levels were measured in all participants, and thyroid hormone and TSH levels were assessed annually during follow-up.
The final multivariate showed that the risk for developing metabolic syndrome grew progressively higher with the gradual increase of FT3 concentrations.
The hazard ratios (95% CI) for metabolic syndrome across increasing quintiles, quartiles, and tertiles of FT3 concentrations were 1.00 (reference), 1.03 (0.84-1.25), 1.14 (0.94-1.38), 1.09 (0.90-1.32), and 1.33 (1.11-1.61), respectively (P for trend <.01). There were no significant associations observed between metabolic syndrome and FT4 and TSH.
“The study is the first cohort study to demonstrate that FT3 within reference range is independently positively associated with the incidence of metabolic syndrome,” the researchers write. “However, the follow-up period of the study is short, and further long-term studies are needed to confirm our results.”
Gu Y, Wang Y, Zhang Q, et al. The association between thyroid function and incidence of metabolic syndrome in euthyroid subjects: Tianjin chronic low-grade systemic inflammation and health cohort study [published online February 17, 2018]. Clin Endocrinol (Oxf). doi:10.1111/cen.13576