Congenital hyperthyroidism is a rare clinical condition, and in most cases, it is a transient disorder caused by maternal Graves disease associated with the transplacental passage of maternal thyroid-stimulating antibodies. Germline mutations of thyrotropin receptor (TSHR) gene determining a constitutive activation of the receptor were identified as a molecular cause of congenital nonautoimmune hyperthyroidism. TSHR gene mutations also cause the familial gestational hyperthyroidism, that is characterized by thyrotoxicosis and hyperemesis gravidarum.
