Radiotherapy of brain tumours given to children and adults is connected with various hormonal dysfunctions later in the life. There are anterior pituitary hormones deficiencies, hyperprolactinemia and precocious puberty. Their severity and frequency depends on the dose applied, age of the radiotherapy and time after radiotherapy. In children, the most important is early recognition of them, with growth hormone deficiency as most common. The impact of cranial irradiation on gonadotrophin secretion may result in precocious puberty and hypogonadism. Other cause of hypogonadism could be a deleterious effect of chemotherapy due to influence both on the pituitary and gonadal hormones secretion. TSH and ACTH deficiencies are less common. The occurrence of radiation-induced anterior pituitary hormonal deficiencies is high, they are progressive and irreversible. So, regular hormonal testing is crucial for early diagnosing of hypopituitarism and replacing of deficient hormones.