Association between lifestyle factors and thyroid function in young euthyroid adults

Purpose:The present work examines the associations of dietary habits,sedentarism,physical activity(PA)levels and sleep habits,with thyroid function in young euthyroid adults.Methods:A total of 105 young euthyroid adults participated in this cross-sectional study.Thyroid function was determined in fasting conditions(>6 h).Dietary habits were measured by a food frequency questionnaire and three non-consecutive 24 h recalls,and different dietary intake and patterns were then estimated.The time spent in sedentary,PA levels and sleep habits were objectively measured using a wrist-worn accelerometer.Results:Energy and carbohydrate intake were positively associated with thyroid stimulating hormone(TSH)(β=0.222;R^(2)=0.102;P=0.022 andβ=0.425;R^(2)=0.129;P=0.007,respectively)whereas fat intake was negatively associated with TSH(β=-0.428;R^(2)=0.137;P=0.004).Energy intake was also positively associated with free triiodothyronine(β=0.277;R^(2)=0.137;P=0.004).Further,adherence to the Mediterranean diet was negatively related to TSH and free thyroxine(FT4)(β=-0.221;R^(2)=0.113;P=0.020 andβ=-0.268;R^(2)=0.071;P=0.007,respectively).Vigorous-intensity and overall PA were negatively associated with FT4(β=-0.227;R^(2)=0.052;P=0.022 andβ=-0.204;R^(2)=0.042;P=0.041,respectively).In contrast,no associations were found between sleep parameters and thyroid function.Conclusions:Lifestyle factors such as dietary intake and PA levels seems to be related to thyroid function even in young euthyroid adults.