The Relationship between Thyroid Hormones, Metabolic Syndrome and HOMA-IR in People with Obesity or Overweight

Objective: In the literature the data about the relationship between thyroid hormone (TH) levels and Metabolic Syndrome (MetS) components are conflicting. Our aim was to evaluate the associations between THs and MetS as well as individual components of MetS and homeostatic model assessment of insulin resistance (HOMA-IR) in euthyroid people with obesity and overweight. Materials and methods: Adult patients who presented to Family Medicine Outpatient Clinics of a tertiary hospital between May 2019 and December 2019 with the intention of weight loss were enrolled in this cross-sectional, descriptive study. The data including height, weight, waist circumference, hip circumference, blood pressure (BP), fasting blood glucose (FBG), total cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglyceride, thyroid stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), insulin, HOMA-IR, and HbA1c were analyzed. Results: A total of 175 patients, 135 (77.1%) female, 40 (22.9%) male (mean age: 40.8 ± 13.1 years), without known thyroid dysfunction were included. A total of 86 were overweight and 89 were obese. Fifty-nine (33.7%) of the study participants were diagnosed with MetS. Subjects with MetS had significantly higher level of fT3 even within the normal range (p = 0.039). When TSH, fT4 and fT3 values were compared with other metabolic components in the group with MetS, a significant positive correlation was found only between fT4 level and HOMA-IR (Rho = 0.316, p = 0.026). Conclusions: MetS was associated with high normal fT3 suggesting differential thyroid hormone metabolism in people with MetS