Subclinical thyroid dysfunction and anemia are common disorders, and both have increasing prevalence numbers with advancing age.
The aim of this study was to assess whether levothyroxine treatment leads to a rise in hemoglobin levels in older persons with subclinical hypothyroidism.
A pre-planned combined analysis of two randomized controlled trials.
Community-dwelling persons aged 65 years and older with subclinical hypothyroidism.
Participants were randomly assigned to levothyroxine or placebo treatment. The dose of levothyroxine was periodically titrated aiming at thyroid stimulating hormone (TSH) level within the reference range and mock titrations in the placebo group.
The main outcome measure was the change in hemoglobin level after 12 months.
Analyses included 669 participants (placebo n=337, levothyroxine n=332) with a median age of 75 years (range 65 to 97) and mean baseline hemoglobin of 13.8±1.3 g/dL. Although levothyroxine treatment resulted in a reduction in TSH from baseline after 12 months of follow-up compared to placebo, the change in hemoglobin level was not different between the levothyroxine and the placebo groups (-0.03 g/dL [95%CI -0.16 to 0.11]). Similar results were found in stratified analyses including sex, age or TSH levels. No difference in change of hemoglobin levels after 12 months was identified in 69 participants with anemia at baseline (-0.33 g/dL [95% CI -0.87 to 0.21]).
In persons aged 65 years and older with subclinical hypothyroidism, treatment with levothyroxine does not lead to a rise in hemoglobin levels, regardless of the presence of anemia.

© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society.