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Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4.

ABSTRACT: Background:It is unclear whether variations in thyroid status within or near the reference range affect energy expenditure, body mass, or body composition. Methods:138 subjects treated with levothyroxine (LT4) for hypothyroidism with normal TSH levels underwent measurement of total, resting, and physical activity energy expenditure; thermic effect of food; substrate oxidation; dietary intake; and body composition. They were assigned to receive an unchanged, higher, or lower LT4 dose in randomized, double-blind fashion, targeting one of three TSH ranges (0.34 to 2.50, 2.51 to 5.60, or 5.61 to 12.0 mU/L). The doses were adjusted every 6 weeks to achieve target TSH levels. Baseline measures were reassessed at 6 months. Results:At study end, the mean LT4 doses and TSH levels were 1.50 ± 0.07, 1.32 ± 0.07, and 0.78 ± 0.08 µg/kg (P < 0.001) and 1.85 ± 0.25, 3.93 ± 0.38, and 9.49 ± 0.80 mU/L (P < 0.001), respectively, in the three arms. No substantial metabolic differences in outcome were found among the three arms, although direct correlations were observed between decreases in thyroid status and decreases in resting energy expenditure for all subjects. The subjects could not ascertain how their LT4 dose had been adjusted but the preferred LT4 dose they perceived to be higher (P < 0.001). Conclusions:Altering LT4 doses in subjects with hypothyroidism to vary TSH levels in and near the reference range did not have major effects on energy expenditure or body composition. Subjects treated with LT4 preferred the perceived higher LT4 doses despite a lack of objective effect. Our data do not support adjusting LT4 doses in patients with hypothyroidism to achieve potential improvements in weight or body composition.

SUBMITTER: Samuels MH

PROVIDER: S-EPMC6194808 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4.

Samuels Mary H MH Kolobova Irina I Niederhausen Meike M Purnell Jonathan Q JQ Schuff Kathryn G KG

The Journal of clinical endocrinology and metabolism 20181101 11

<h4>Background</h4>It is unclear whether variations in thyroid status within or near the reference range affect energy expenditure, body mass, or body composition.<h4>Methods</h4>138 subjects treated with levothyroxine (LT4) for hypothyroidism with normal TSH levels underwent measurement of total, resting, and physical activity energy expenditure; thermic effect of food; substrate oxidation; dietary intake; and body composition. They were assigned to receive an unchanged, higher, or lower LT4 do ...[more]

PMID: 30165520

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Project description:BackgroundTotal energy expenditure (TEE) data in patients with early-stage cancer are scarce, precluding an understanding of energy requirements.ObjectiveThe objective was to cross-sectionally characterize TEE in patients with colorectal cancer (CRC) and to compare measured TEE with energy recommendations. It was hypothesized that TEE would differ according to body mass, body composition, and physical activity level (PAL) and current energy recommendations would have poor individual-level accuracy.MethodsPatients with newly diagnosed CRC had resting energy expenditure (REE) measured by indirect calorimetry and TEE by doubly labeled water. Hypermetabolism was defined as REE > 110% of that predicted from the Mifflin St.-Jeor equation. Body composition was assessed via DXA. Physical activity was determined as the ratio of TEE to REE (TEE:REE) (PAL) and residual activity energy expenditure (RAEE). TEE was compared with energy recommendations of 25-30 kcal/d and Dietary Reference Intakes (DRIs) using Bland-Altman analyses. Patients were stratified according to median BMI, PAL, and sex-specific ratio of fat mass (FM) to fat-free mass (FFM).ResultsTwenty-one patients (M:F 14:7; mean ± SD BMI: 28.3 ± 4.9 kg/m2, age: 57 ± 12 y) were included. Most (n = 20) had stage II-III disease; 1 had stage IV. Approximately half (n = 11) were hypermetabolic; TEE was not different in those with hypermetabolism and REE as a percentage of predicted was not correlated with TEE. Mean ± SD TEE was 2473 ± 499 kcal/d (range: 1562-3622 kcal/d), or 29.7 ± 6.3 kcal/kg body weight (range: 20.4-48.5 kcal/kg body weight). Mean ± SD PAL was 1.43 ± 0.27. The energy recommendation of 25 kcal/kg underestimated TEE (-12.6% ± 16.5%, P = 0.002); all energy recommendations had wide limits of agreement (the smallest was DRI with measured PAL: -21.2% to 29.3%). Patients with higher BMI and FM:FFM had higher bias using kilocalories per kilogram recommendations; bias from several recommendations was frequently lower (i.e. underestimation) in patients with higher PAL and RAEE.ConclusionsTEE variability was not reflected in energy recommendations and error was related to body weight, body composition, and physical activity. This trial was registered at clinicaltrials.gov as NCT03131921.

Dataset Information

Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4.

Publications

Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4.

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