Endocrine Abstracts

Introduction and aim: Overt thyroid dysfunction is well recognized to affect weight, but the influence of minor perturbations of thyroid function remains unclear. There is ongoing debate regarding the influence of minor changes in thyroid hormones status within the normal range and BMI. The aim of this study was to investigate the association between thyroid function within normal ranges and obesity via BMI and body compositions analyzed by bioelectrical impedance.

Materials and methods: One hundred twenty persons with normal thyroid functions were included in our study. According to the BMI, the patients were divided into 5 groups. Group1; normal weight (n=40), group 2; overweight (n=20), group3; classI obesity (n=20), group4; class II obesity (n=20), group 5 morbid obesity (n=20). Measurements of serum TSH, free T3, free T4 and lipid profile were recorded. Body compositions and BMI were evaluated by bioelectrical impedance (TANITA).

Results: In group 1, TSH was negatively correlated with BMI (r=−0.430, P=0.006). On the contrary, TSH was positively correlated with percentage of body fat (BF%) (r=0.391, P=0.014). Free T3 was positively correlated with BF% (r=0.333, P=0.038). In group 2, free T3 was positively correlated with BF% and fat mass (r=0.657, P=0.010, r=0.751, P<0.001 respectively). In group 3, free T3 was positively correlated with BF%, fat mass, HOMA-IR and LDL (r=0.521, P=0.018; r=0.543, P=0.013; r=0.512, P=0.021; r=0.469, P=0.037, respectively). Similarly, TSH was positively correlated with BMI (r=0.553, P=0.011). In group 5, free T4 was negatively correlated with LDL (r=−0.485, P=0.030).

Conclusion: We demonstrated that differences in thyroid function within the normal range may correlate with differences in BMI and body compositions in subjects within different BMI categories. Further large scale data from the population is required to confirm our findings.