Effects of XXXX Replacement or Suppressive Therapy on Energy Expenditure and Body Composition.

@entity1 @entity1375 @entity1955 @entity2016 @entity1954
BACKGROUND: Thyrotropin (TSH)-suppressive doses of @entity1955 ( @entity2016 ) have adverse effects on bone and cardiac function, but it is unclear whether metabolic function is also affected. The objective of this study was to determine whether @entity1 receiving TSH-suppressive @entity2016 doses have alterations in energy expenditure or body composition. METHODS: This study was a cross-sectional comparison between three groups of @entity1 : 26 @entity1 receiving chronic TSH-suppressive @entity2016 doses, 80 @entity1 receiving chronic replacement @entity2016 doses, and 16 untreated euthyroid control @entity1 . Subjects underwent measurements of resting energy expenditure (REE), substrate oxidation, and thermic effect of food by indirect calorimetry; physical activity energy expenditure by accelerometer; caloric intake by 24-hour diet recall; and body composition by dual X-ray absorptiometry. RESULTS: REE per kilogram lean body mass in the @entity2016 euthyroid @entity1 was 6% lower than that of the @entity2016 -suppressed group, and 4% lower than that of the healthy control group (p   =   0.04). Free @entity1954 (fT3) levels were directly correlated with REE, and were 10% lower in the @entity2016 euthyroid @entity1 compared with the other two groups (p   =   0.007). The groups of subjects did not differ in other measures of energy expenditure, caloric intake, or body composition. CONCLUSIONS: @entity2016 suppression therapy does not adversely affect energy expenditure or body composition in @entity1 . However, @entity2016 replacement therapy is associated with a lower REE, despite TSH levels within the reference range. This may be due to lower fT3 levels, suggesting relative tissue @entity1375 may contribute to impaired energy expenditure in @entity2016 therapy.
