[Hypothalamo-hypophyseal function after treatment of cancers]

Cranial irradiation may result in altered hypothalamo-pituitary function in patients treated for cancer distant from this area. Growth hormone (GH) deficiency is the most frequent complication. The frequency, delay of occurrence and severity of GH deficiency depend on the irradiation dose delivered to this area. The other factors influencing the frequency are the age at irradiation and the fractionation schedule. The frequency of other hypothalamo-pituitary changes is also dose-dependent: thyrotropin and gonadotropin deficiencies occur in 50-60% of cases after 50 Gray, and corticotrophin deficiency in 30%. Low dose cranial irradiation may also induce precocious puberty (onset < 8 yr in girls and < 10 yr in boys). The radiation-induced lesions seem to occur in the hypothalamus rather than in the pituitary. There is generally a good correlation between the GH peak and the growth velocity, but there may be normal growth in spite of GH deficiency after low dose or due to precocious puberty, decreased growth velocity in spite of normal GH peak, due to bone irradiation. Results on final height have been optimized by a better indication of GH therapy and by its association with treatment of precocious puberty.