Thyroid Science 4(3):C1-12, 2009

Stability, Effectiveness, and Safety of
Desiccated Thyroid vs Levothyroxine:
A Rebuttal to the British Thyroid Association

Dr. John C. Lowe
Director of Research:
Fibromyalgia Research Foundation

Full text free: pdf format

Abstract. In 2007, an Executive Committee (the Committee) of the British Thyroid Association (BTA) published a document in which it concluded that levothyroxine is safer, more stable, and more effective than Armour Thyroid. By extension, the conclusion also applies to other natural desiccated thyroid (NDT) products, such as Nature-Throid and Westhroid. Enough evidence is available, however, to conclude that T4/T3 therapies with either synthetic hormones or NDT are safer and more effective than T4 replacement, and that NDT is more stable than levothyroxine products. The Committee mentioned clinical trials that directly bear on its conclusions, but it did not include any of these in the reference section of its document. Instead, it referenced a review of the clinical trials by Escobar-Morreale et al. and a meta-analysis of the trials by Grozinsky-Glasberg et al. These two publications, however, deal with synthetic T4/T3 therapies, not NDT. Both publications contain factual errors and unbalanced presentations of data, excluding or limiting data favorable to T4/T3 therapies. Specific examples from the publications are included in this rebuttal. The unbalanced data presentations and factual errors of Escobar-Morreale et al. and Grozinsky-Glasberg et al. may have influenced the Committee’s conclusions. Nonetheless, the Committee’s document contains false statements and unbalanced presentations of data independent from those in the other authors’ publications. Specific examples are included in this rebuttal. The Committee, the BTA, Escobar-Morreale et al., and Grozinsky-Glasberg et al. are all called upon to correct their false statements of fact as well as their unbalanced presentations of data relevant to their conclusions.

Keywords. Armour Thyroid • British Thyroid Association • FDA • Levothyroxine • Levoxyl • Natural desiccated thyroid • Nature-Throid • Synthroid • Westhroid