Association between thyroid hormone levels, body composition and insulin resistance in euthyroid subjects with normal thyroid ultrasound: The Kangbuk Samsung Health Study.

Lower SMI was significantly associated with higher serum FT3 levels, the active form of thyroid hormone, in both men and women. Higher insulin resistance was positively associated with serum FT3 levels and inversely associated with serum TSH levels in euthyroid subjects with normal thyroid US findings.