Levothyroxine fails to prevent pregnancy loss in women with TPO antibodies

  • Dhillon-Smith RK & al.
  • N Engl J Med
  • 23 Mar 2019

  • International Clinical Digest
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Takeaway

  • Levothyroxine (Synthroid, Tirosint, Levoxyl) failed to improve live-birth rates in euthyroid women with preconception thyroid peroxidase (TPO) in a UK randomized controlled trial.

Why this matters

  • TPO antibodies are associated with increased risk for miscarriage and preterm birth, and levothyroxine treatment had previously shown efficacy for preventing these outcomes in small trials.

Key results

  • Pregnancy rate was not statistically different with levothyroxine vs placebo (56.6% vs 58.3%; relative risk [RR], 0.97; 95% CI, 0.88-1.07).
  • Levothyroxine and placebo were associated with similar live-birth rates at ≥34 weeks (primary outcome; 37.4% vs 37.9%; RR, 0.97; P=.74).
  • Levothyroxine and placebo were also associated with similar rates of miscarriage at

Study design

  • 952 women with TPO antibodies and a history of miscarriage or infertility were randomly assigned to receive levothyroxine (50 μg once daily; n=476) or placebo (n=476) before conception through the end of pregnancy.
  • Funding: UK NIHR Efficacy and Mechanism Evaluation Program.

Limitations

  • Dosing may not have been sufficient to observe an effect.