Human chorionic gonadotropin bears structural homology to pituitary thyrotropin. The extremely elevated levels of human chorionic gonadotropin in patients with molar pregnancy or other trophoblastic diseases can lead to hyperthyroidism. We describe a patient with molar pregnancy who had secondary hyperthyroidism prepared rapidly by plasmapheresis for surgery. The clinical picture improved dramatically after the first plasmapheresis. Three subsequent plasmapheresis provided a 75.1% decrease in serum free T3 concentrations and 63.9 / free T4 concentrations and recovery after evacuation. This is the first use of plasmapheresis in rapid preparation of a patient who had secondary hyperthyroidism due to molar pregnancy. (c) 2006 Published by Elsevier Ltd.