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Does combination T4 and T3 therapy make sense?

Michael T McDermott1

  • 1Endocrinology and Diabetes Practice, University of Colorado School of Medicine, Aurora, Colorado 80045, USA. Michael.mcdermott@ucdenver.edu

Endocrine Practice : Official Journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists
|May 3, 2012
PubMed
Summary

Combination therapy with levothyroxine and liothyronine may benefit some hypothyroidism patients with a specific genetic polymorphism. Most patients achieve symptom relief with levothyroxine alone, but persistent symptoms warrant further investigation.

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Area of Science:

  • Endocrinology
  • Pharmacogenomics

Background:

  • Levothyroxine is the standard treatment for hypothyroidism.
  • Some patients experience persistent symptoms despite adequate levothyroxine therapy.
  • The role of combination therapy with liothyronine is debated.

Purpose of the Study:

  • To evaluate the evidence for combined levothyroxine and liothyronine therapy in hypothyroidism.
  • To identify patient subgroups who may benefit from combination therapy.

Main Methods:

  • Systematic review of 11 randomized controlled trials.
  • Inclusion of basic and clinical research findings.
  • Analysis of deiodinase 2 (D2) enzyme polymorphisms.

Main Results:

  • Initial studies suggested benefits of combination therapy.
  • Subsequent trials showed no consistent subjective or objective improvement.
  • A D2 Thr92Ala polymorphism was identified in ~16% of patients.
  • Patients with this polymorphism showed greater symptom improvement with combination therapy.

Conclusions:

  • Most hypothyroidism patients respond well to levothyroxine monotherapy.
  • Persistent symptoms in some patients require investigation for other causes.
  • A subset of patients with the D2 Thr92Ala polymorphism may benefit from combined levothyroxine and liothyronine therapy.