In the article the authors present the case of a patient with clear cell renal carcinoma, where after nephrectomy local metastases appeared. The treatment of choice was sunitinib. After 20 cycles of therapy heavy hypothyroidism was verified which required substitution by thyroxine. Elevated levels of TSH appeared in up to 70% and hypothyrodism in up to 40% of thus treated patients. Also described is the mechanism of action of sunitinib. There seems to exist a correlation between the "adverse effects" of the drug and a better result of the therapy of cancer, however, prospective studies are absent. Most experts agree that the thyroid function during treatment with sunitinib needs to be monitored.

2 interní oddelení FN Na Bulovce Praha