Evaluation of the Association between Insulin Resistance and Subclinical Hypothyroidism Using Triglyceride-Glucose Index: a Cross-Sectional Study.

Abstract

Background: Thyroid disorders and diabetes mellitus are often known to co-exist, implying an interrelationship between thyroid dysfunction and insulin resistance. Triglyceride-glucose (TyG) index is a relatively new surrogate marker of insulin resistance, which is cost-effective and easily calculated with routine lab tests. Data about association of subclinical hypothyroidism (SCH) and insulin resistance, especially with reference to TyG index, is lacking.

Objectives: To evaluate the association of SCH and insulin resistance using the TyG index by comparing its value in patients with SCH and age- and gender-matched euthyroid controls. Also, to determine if there is a correlation between TyG index values and thyroid profile parameters (TSH, FT3 and FT4) in both study groups.

Materials and methods: Thirty-five patients with SCH and an equal number of age- and gender-matched euthyroid controls were included in the present study. The TyG index was calculated for each group and compared. The correlation between TyG index and thyroid profile parameters (TSH, FT3 and FT4) was also assessed.

Results: The TSH values were significantly higher in the SCH group (6.6±1.7 µIU/mL) than the control one (2.5±1.2 µIU/mL; p<0.0001). There was no significant difference in FT3 in the SCH group (2.93±0.49 pg/ mL) and the control one (3.05±0.64 pg/mL; p=0.310). The level of FT4 was also not found to be significantly different in SCH subjects (1.23±0.44 ng/dL) and controls (1.4±0.42 ng/dL; p=0.077). The TyG index values were significantly higher in the SCH group (4.8±0.2) as compared to the control one (4.7±0.2; p = 0.015). The TyG index did not show any significant correlation with the thyroid parameters in any of the two groups.

Conclusion: There is a positive association between SCH and insulin resistance in terms of TyG index. This index may thus be helpful in early screening and management of such patients for insulin resistance related conditions like diabetes mellitus, metabolic syndrome and cardiovascular disorders.