Thyroxine Preparations

Excerpt

To the editor: Over the past decade a minor controversy has raged among thyroidologists in regard to the reasons underlying the observed variations in serum thyroxine concentrations in patients taking different preparations of synthetic L-thyroxine (1-3). The clinical significance of such variation lies in the risk of either iatrogenic thyrotoxicosis on the one hand or inadequate thyrotrophin suppression (in patients with history of thyroid cancer) on the other. Possible explanations for the observed variation have included differences in tablet content or methods of formulation that could influence tablet dissolution and, ultimately, bioavailability. In the May issue of the Annals, Sawin