Sium Wolde Sellasie, Nicola Ossola, Tommaso Piticchio, Luigi Uccioli, Pierpaolo Trimboli
Twenty-three studies including 763 patients were analyzed.Levothyroxine treatment was associated with significant reductions in BW (-1.39 kg; 95% CI: -2.56 to -0.23),BMI (-0.39 kg/m²; 95% CI: -0.68 to -0.11), FM (-0.75 kg; 95% CI: -1.47 to -0.02), and LBM (-0.95 kg; 95% CI: -1.47 to -0.43). Subgroup analyses showed significant reductions in BW and BMI in overt hypothyroidism, but not in subclinical hypothyroidism. Conversely, LBM decreased significantly only in subclinical hypothyroidism. Baseline TSH and study duration were not associated with changes in anthropometric outcomes.
BACKGROUND: Weight gain is commonly regarded as a hallmark of hypothyroidism,although supporting evidence is limited. Consequently, restoration of euthyroidism with levothyroxine is often expected to induce clinically meaningful weight loss or return to premorbid body weight. These expectations may affect patient counseling, treatment satisfaction, and interpretation of persistent symptoms after biochemical correction. This systematic review and metanalysis aimed to synthesize available evidence on changes in body weight(BW) and anthropometric parameters, including body mass index(BMI), waist circumference(WC), fat mass(FM), and lean body mass(LBM), after levothyroxine treatment in hypothyroid adults achieving euthyroidism.
METHODS: A comprehensive search of PubMed and Google Scholar was conducted up to April 1, 2026, to identify original English-language studies reporting anthropometric outcomes before levothyroxine initiation and after achievement of euthyroidism. For each outcome, effect size was calculated as mean change from baseline to post-treatment. When appropriate, heterogeneity was explored through subgroup analyses or meta-regression.
RESULTS: Twenty-three studies including 763 patients were analyzed.Levothyroxine treatment was associated with significant reductions in BW (-1.39 kg; 95% CI: -2.56 to -0.23),BMI (-0.39 kg/m²; 95% CI: -0.68 to -0.11), FM (-0.75 kg; 95% CI: -1.47 to -0.02), and LBM (-0.95 kg; 95% CI: -1.47 to -0.43). Subgroup analyses showed significant reductions in BW and BMI in overt hypothyroidism, but not in subclinical hypothyroidism. Conversely, LBM decreased significantly only in subclinical hypothyroidism. Baseline TSH and study duration were not associated with changes in anthropometric outcomes.
DISCUSSION: Achieving euthyroidism with levothyroxine produces modest reductions in BW, BMI, FM, and LBM. Effects appear partly influenced by disease severity, with more consistent BW and BMI reductions in overt hypothyroidism. These findings support realistic counseling and discourage levothyroxine use solely for weight loss.