Hyperplacentosis: A novel cause of hyperthyroidism

Human chorionic gonadotropin (hCG), which is capable of thyrotropic activit y, is believed responsible for the hyperthyroidism of gestational trophobla stic disease and hyperemesis gravidarum. Hyperplacentosis is a condition of heightened trophoblastic activity characterized by increased placental wei ght and circulating hCG levels higher than those associated with normal pre gnancy. We report the first case of hyperthyroidism associated with hyperpl acentosis. Correction of the hyperthyroidism occurred after hysterotomy and correlated with declining hCG levels. Hyperplacentosis should be included among the causes of hCG-mediated hyperthyroidism.