Relationship between thyroid function tests and bioelectrical impedance measurement parameters according to degree of obesity

Abstract

Aims: This study aimed to investigate the relationship between thyroid function tests and bioelectrical impedance measurement parameters showing body composition in groups of patients with varying degrees of obesity as determined by body mass index (BMI). Methods: A total of 120 people between the ages of 18 and 65 years were enrolled in the study, including 20 individuals with stage 1 obesity, 20 with Stage 2 obesity, 20 with Stage 3 obesity, and 40 with normal body weights. In the collection of data, a case report form prepared by the researcher for gathering information about the participants and the results of blood tests and bioelectrical impedance measurements made with a Tanita device were used. Blood samples were taken from the antecubital vein between 09:00 and 10:00 in the morning after at least 8 hours of fasting. HOMA-IR values were calculated by measuring fasting plasma glucose and insulin. Results: No significant correlation was found between median BMI and TSH, fT3 and fT4 levels in the whole population. While a negative correlation was found between median TSH and BMI in the group with normal body weight (r=-0.430, p=0.006), a positive correlation was found in the Stage 1 obese group (r=0.553, p=0.011). This relationship was not significant in the Stage 2 and morbidly obese groups. There was no significant correlation between BMI and fT4 and fT3 in all groups. A positive correlation was found between fat percentage and TSH (r=0.391, p=0.014) and fT3 (r=0.333, p=0.038) levels in the group with normal body weight, while no correlation was found with T4 levels. Conclusion: No statistically significant differenceswere found in terms of thyroid functions in different obesity classes as determined by BMI. Elevations of thyroid-stimulating hormone in obese patients are thought to be a result of obesity, not the cause.