An unusual case of central hypothyroidism and thyrotoxicosis factitia

Thyrotoxicosis factitia can be quite difficult to diagnose and manage. This report describes an unusual case in a patient with bulimia who initially presented with central hypothyroidism. A spectrum of central hypothyroidism alternating with marked hyperthyroidism was found to be the result of periodic ingestion of massive doses (12-24 mg) of a veterinarian preparation of L-thyroxine. The patient's clinical course demonstrates the tolerance of serum levels of thyroxine as high as 244 to 330 mu g/dL without requiring acute medical intervention and a prolonged 2- to 3-month period of central hypothyroidism after discontinuation of L-thyroxine. Supplements intended for livestock and pets may provide a previously underrecognized and particularly dangerous source for thyroid hormone abusers.