Association between lifestyle factors and thyroid function in young euthyroid adults

The present work examines the associations of dietary habits, sedentarism, physical activity (PA) levels and sleep habits, with thyroid function in young euthyroid adults.

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.

Energy and carbohydrate intake were positively associated with thyroid stimulating hormone (TSH) (β = 0.222; R² = 0.102; P = 0.022 and β = 0.425; R² = 0.129; P = 0.007, respectively) whereas fat intake was negatively associated with TSH (β = −0.428; R² = 0.137; P = 0.004). Energy intake was also positively associated with free triiodothyronine (β = 0.277; R² = 0.137; P = 0.004). Further, adherence to the Mediterranean diet was negatively related to TSH and free thyroxine (FT4) (β = −0.221; R² = 0.113; P = 0.020 and β = −0.268; R² = 0.071; P = 0.007, respectively). Vigorous-intensity and overall PA were negatively associated with FT4 (β = −0.227; R² = 0.052; P = 0.022 and β = −0.204; R² = 0.042; P = 0.041, respectively). In contrast, no associations were found between sleep parameters and thyroid function.

Lifestyle factors such as dietary intake and PA levels seems to be related to thyroid function even in young euthyroid adults.