TY - JOUR
T1 - Effects of altering levothyroxine dose on energy expenditure and body composition in subjects treated with LT4
AU - Samuels, Mary H.
AU - Kolobova, Irina
AU - Niederhausen, Meike
AU - Purnell, Jonathan Q.
AU - Schuff, Kathryn G.
N1 - Publisher Copyright:
Copyright © 2018 Endocrine Society.
PY - 2018
Y1 - 2018
N2 - 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 6 0.07, 1.32 6 0.07, and 0.78 6 0.08 mg/kg (P, 0.001) and 1.85 6 0.25, 3.93 6 0.38, and 9.49 6 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.
AB - 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 6 0.07, 1.32 6 0.07, and 0.78 6 0.08 mg/kg (P, 0.001) and 1.85 6 0.25, 3.93 6 0.38, and 9.49 6 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.
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U2 - 10.1210/jc.2018-01203
DO - 10.1210/jc.2018-01203
M3 - Article
C2 - 30165520
AN - SCOPUS:85055147395
SN - 0021-972X
VL - 103
SP - 4163
EP - 4175
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 11
ER -