Thyrotoxicosis in neonates is a very rare disease. It develops prenatally and is associated with thyrotoxicosis of the mother. However only 1 - 2 % children born to thyrotoxic mothers suffer from the disease. The cause is transplacental transmission of maternal antibodies which stimulate the thyrotropin (TSH) receptor (rTSH-ab). The greatest risk for the development of neonatal thyrotoxicosis are high maternal rTSH-ab titres during the last trimester of pregnancy. During the foetal period thyrotoxicosis of the foetus may be manifested by tachycardia, intrauterine growth retardation, possible goitre, and it may cause foetal death. The disease may have a serious course in the neonate with a significant mortality (as high as 25 %) unless diagnosed in time. Usually it recedes, however, as the levels of maternal antibodies decline. Rarely a persisting non-autoimmune form of neonatal thyrotoxicosis is encountered due to activating mutation of the TSH receptor (t-TSH) or activating mutation of the alpha-subunit of G protein which transmits the signal of the TSH receptor. In the case-report the authors describe a case of neonatal thyrotoxicosis caused by transplacental transfer of antibodies.

        Key words: neonatal thyrotoxicosis, causes, symptoms, treatment, prognosis