[Late effects of radiotherapy on the neuroendocrine system]

When the hypothalamic-pituitary axis (HPA) is included in the treatment field in children and adults, a variety of neuroendocrine disturbances are more common than has been appreciated in the past. Clinical damage to the pituitary and thyroid glands usually occurs months to years after treatment, and is preceded by a long subclinical phase. Primary brain tumors represent the largest group of malignant solid tumors in children. The survival rates of 50% reported in the literature are achieved at the expense of late occurring effects. Radiation-induced abnormalities are generally dose-dependent. Growth hormone deficiency and premature sexual development can occur at doses as low as 18 Gy in conventional fractionation, and is the most common neuroendocrine problem in children. In patients treated with > 40 Gy on the HPA, deficiency of gonadotropins, thyroid stimulating hormone, and adrenocorticotropin can be found. Following high-dose radiotherapy (> 50 Gy), hyperprolactinemia can be seen, especially among young women. Most neuroendocrine disturbances that develop as a result of HPA can be treated efficiently, provided that an early detection of these endocrine dysfunctions abnormalities is done.