Correlation of Thyroid Hormone Levels and Sensitivity With Metabolic Syndrome in Older Adults

Previous studies have shown that thyroid function is associated with metabolic syndrome (MetS), but this association remains poorly understood in older adults. This study aimed to explore the relationships between thyroid hormone levels and sensitivity with MetS and its components in older adults.

The 2018 baseline data of the West China Health and Aging Trends study were used. MetS was diagnosed according to the International Diabetes Federation definition. Central thyroid hormone sensitivity was assessed by the TSH Index (TSHI), Thyrotrophic T4 Resistance Index (TT4RI), Thyroid Feedback Quantile-based Index (TFQI), and Parametric TFQI (PTFQI). Peripheral thyroid hormone sensitivity was assessed by the FT3 to FT4 ratio (FT3/FT4 ratio).

A total of 3796 participants were included. The prevalence of MetS was 40.31%. High FT3 levels and FT3/FT4 ratios were associated with abdominal obesity and hypertension; decreased FT3 levels were associated with hyperglycemia, hypertriglyceridemia and low HDL-C; low FT4 levels were associated with abdominal obesity and hypertriglyceridemia; increased TSH, TSHI and TT4RI levels were associated with hypertriglyceridemia and hypertension; and increased TFQI and PTFQI were associated with hypertension (p < 0.05, for all). Increased FT3 (OR = 1.13, 95% CI: 1.05-1.22), TSH (OR = 1.12, 95% CI: 1.04-1.20), TSHI (OR = 1.09, 95% CI: 1.01-1.17), TT4RI (OR = 1.09, 95% CI: 1.01-1.16), FT3/FT4 (OR = 1.25, 95% CI: 1.16-1.35) and low FT4 (OR = 0.87, 95% CI: 0.81-0.94) were associated with MetS.

Thyroid hormone levels are correlated with MetS and its components. Reduced central thyroid hormone sensitivity and increased peripheral thyroid hormone sensitivity are risk factors for MetS in older adults.