The case report focuses on the case of heavy Graves - Basedow thyreotoxicosis in 33 years old secundipara who was transferred to our departement from regional hospital for decompensation of gestational hypertension, oligohydramnios and the suspition on intrauterine growth restriction (IUGR). In our clinical praxis the problems of thyroid gland in terms of its reduced function in pregnant women are getting more frequent. The goal of this article is to describe the less often situation, the hyperthyroidism in the third trimestr of the pregnancy. Thyretoxicosis in pregnancy is associated with higher risk of preterm labour, preeclampsia, IUGR, heart failure and stillbirth. Some of these complications confirmes our case report.