Thyrotoxicosis due to Ingestion of Excess Thyroid Hormone*

THE TERM thyrotoxicosis factitia has been used to describe thyrotoxicosisinduced by ingestion of excess thyroid hormone (1). This entity has also been termed alimentary or exogenous thyrotoxicosis (2, 3), occult factitial thyrotoxicosis (4), and thyreoidismus medicamentosus (5). As they imply, these terms describe the various reasons why excess thyroid hormone is ingested. These include not only the ingestion of excess thyroid hormone by individuals with unstable psychiatric profiles, but also administration of excess thyroid hormone to volunteers including students (6) and prisoners (7) in an effort to produce thyrotoxicosis for research studies. The hormone has been ingested both intentionally (8–16) and unintentionally (5, 17) in diet pills and in ground beef contaminated with bovine thyroid tissue (18, 19). The accidental ingestion of large quantities of medication by children and, less frequently, by adults, is another cause of thyrotoxicosis factitia. The thyroid gland is unique among the endocrine glands because of its large store of preformed hormone. Furthermore, the peripheral turnover of the two major iodothyronines, T4 and T3, is relatively slow, 6.7 days and 1 day, respectively, due primarily to the tight binding of the hormones to circulating plasma proteins (20, 21).