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February 8, 1980

Hormonal Content of Thyroid Replacement Preparations

JAMA. 1980;243(6):549-550. doi:10.1001/jama.1980.03300320041023

ACCORDING to present pharmaceutical industry estimates, there were 15 million prescriptions written in the last year for thyroid replacement in the United States. Of these, approximately 50% were for synthetic hormones, and the remainder were for preparations derived from animal sources. At present, both generic thyroid and levothyroxine preparations are available, and their use has been encouraged by recent changes in prescription regulations. Since the Food and Drug Administration still accepts the United States Pharmacopeia standard based on organic iodine content for this medication, there is no specification of the precise hormonal content of these tablets. This study reports the triiodothyronine (T3) and thyroxine (T4) content of a number of generic thyroid and T4 preparations, using a radioimmunoassay.1 This survey was occasioned by the experience of a patient who received a biologically ineffective thyroid tablet.

Report of a Case  A 54-year-old woman with primary hypothyroidism since