A modification of the Leland and Foster method for estimation of the thyroxine-like fraction in thyroid materials is described. This chemical method can be used to identif commercial thyroid preparations which are defective by clinical evaluation or by &ological assay. In contrast, no difference in the content of the thyroxinelike fraction of effective and defective thyroid samples could be shown by our use of Blau's method.
ECENTLY we have found that certain batches and brands of thyroid tablets were relatively ineffective in the treatment of hypothyroidism in agreement with other recent reports (1, 2). Except for a British Pharmacopoeia preparation, all material clinically studied had been standardized in accordance with U.S.P. requirements. Unusually large daily amounts of these defective preparations were needed by patients who nevertheless responded at least as well to the customary small daily doses of other lot numbers or brands of thyroid. Since it was apparent that the defective thyroid tablets contained excessive amounts of nonhormonal iodinated compounds, quantitation of the hornonally active fraction might be useful in the identification of "ineffective" thyroid preparations.
Leland and Foster (3) described a method for the determination of the thyroxine content in an alkaline hydrolysate of large quantities (1 Gm.) of desiccated thyroid. We have modified the Leland and Foster method by using the sealedtube alkaline hydrolysis procedure of Kennedy (4) for which only small amounts to 2 grains) of thyroid material are required. The iodinated compounds in the hydrolysate are extracted into n-butanol and a small portion of the butanol extract, after backwashing with alkali, is analyzed directly for iodine content using a procedure modified from Bodansky, et al. (5). The iodide-