Is resting energy expenditure affected by tsh in euthyroid patients?

Thyroid dysfunctions are associated with changes in body weight and composition, body temperature, and resting energy expenditure (REE). Evidence suggests that also slight variations in TSH values within reference ranges contribute to the obesity and the tendency to gain weight, although this has not been confirmed by all studies. The aim of our study is to evaluate if minimal differences in TSH in euthyroid patients can influence REE and obesity. Patients with TSH between 0.2 mIU/l and 4.2 mIU/l were considered euthyroid and were enrolled in the study. The REE was measured (REE m) by indirect calorimetry and compared with REE predicted (REE p) by Harris Benedict equation. 2340 subjects (71.3% females, 45.8 ± 13.1 years, BMI= 29.4 ± 5.5) were included. Mean TSH of the sample was 1.91 ± 0.83 mIU/l. The subjects were grouped according to TSH concentration quartiles. No significant differences were observed in the prevalence of hypometabolic subjects (REE m< REE p) between highest and lowest TSH quartiles ( 62.2% vs 65%, p= 0.7). The mean delta % REE resulted similar between highest and lowest TSH quartiles (8.4% vs 7.9%, p= 0.17). Moreover the prevalence of obesity (BMI>29.9 kg/m2) was not significantly higher in the highest vs lowest TSH quartiles (41.8% vs 40.1%, p= 0.8). Conclusions: our findings showed that modest variations in TSH values in euthyroid patients don't increase the prevalence of hypometabolism and obesity.