Eur J Endocrinol. 2009 Oct 6. [Epub ahead of print]
Do we need still more trials on T4 and T3 combination therapy in hypothyroidism?
Wiersinga W. W Wiersinga, Endocrinology & Metabolism, AMC, Amsterdam, 1105 AZ, Netherlands.
Approximately 10% of hypothyroid patients are dissatisfied with the outcome of levothyroxine replacement. It is unlikely that slight over- or under-treatment with T4 explains remaining complaints. Meta-analysis of randomized clinical trials shows no advantage of T4/T3 combination therapy over T4 monotherapy. However, each of these trials can be criticized, and none is perfect: most of them failed to mimick the physiological ratio of serum FT4 to FT3 concentrations. Development of a sustained-release T3 preparation given as a single night-time dose (together with levothyroxine once daily) might maintain physiological serum FT4 to FT3 ratio's throughout 24 hours. Genetic polymorphisms in deiodinase 2 and thyroid hormone transporters have been associated with well-being, fatigue, depression and greater improvement on combination therapy. Future trials should aim at carriers of these polymorphisms to see if they do better on T4/T3 combination therapy than on T4 monotherapy.
PMID: 19808902 [PubMed - as supplied by publisher]