Association between thyroid hormones, insulin resistance, and metabolic syndrome

OBJECTIVE: To determine the association between thyroid hormones, insulin resistance, and metabolic syndrome in euthyroid women.

METHODS: Forty-five women with no past medical history were studied in this cross-sectional study at the Department of Endocrinology, Medwin Hospitals, Hyderabad, India, from August 2008 to September 2008. The body fat was estimated using bio-impedance method, and fasting blood sample was analyzed for total triiodothyronine (T3), total thyroxine (T4), thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), lipid profile, insulin, and glucose.

RESULTS: The mean age of the participants was 32.6 +/= 9.6 years with a body mass index (BMI) of 29.9 +/= 3.8 kg/m2. Evidence of homeostasis model assessment index for insulin resistance (HOMA-IR) more than 3 was seen in 34 (75%) and metabolic syndrome in 29 (64%) participants. Total T3 showed a positive correlation with triglycerides, low density lipoprotein- cholesterol (LDL-C), total cholesterol, insulin, HOMA-IR and negatively with body fat. Thyroid-stimulating hormone correlated positively with BMI, insulin, HOMA-IR, LDL-C and negatively with HDL-cholesterol (p<0.05). Free triiodothyronine correlated positively with waist circumference and T4 did not correlate with metabolic syndrome parameters.

CONCLUSION: Our preliminary data show an association between thyroid hormones and some components specific of the metabolic syndrome in euthyroid women. Total triiodothyronine and TSH correlated more with variables of metabolic syndrome than FT3 and T4.