title: Effect of growth hormone-releasing factor on growth hormone release in children with radiation-induced growth hormone deficiency.
abstract: Five male children who received cranial irradiation for extrahypothalamic intracranial neoplasms or leukemia and subsequently developed severe growth hormone (GH) deficiency were challenged with synthetic growth hormone-releasing factor (GRF-44), in an attempt to distinguish hypothalamic from pituitary dysfunction as a cause of their GH deficiency, and to assess the readily releasable GH reserve in the pituitary. In response to a pulse of GRF-44 (5 micrograms/kg intravenously), mean peak GH levels rose to values higher than those evoked by the pharmacologic agents L-dopa or arginine (6.4 +/- 1.3 ng/mL v 1.5 +/- 0.4 ng/mL, P less than .05). The peak GH value occurred at a mean of 26.0 minutes after administration of GRF-44. These responses were similar to those obtained in children with severe GH deficiency due to other etiologies (peak GH 6.3 +/- 1.7 ng/mL, mean 28.0 minutes). In addition, there was a trend toward an inverse relationship between peak GH response to GRF-44 and the postirradiation interval. Prolactin and somatomedin-C levels did not change significantly after the administration of a single dose of GRF-44. The results of this study support the hypothesis that cranial irradiation in children can lead to hypothalamic GRF deficiency secondary to radiation injury of hypothalamic GRF-secreting neurons. This study also lends support to the potential therapeutic usefulness of GRF-44 or an analog for GH deficiency secondary to cranial irradiation.
mesh_terms: D000293:Adolescent; D001932:Brain Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D004393:Dwarfism, Pituitary / Q000097:blood; D013006:Growth Hormone / Q000097:blood / Q000172:deficiency*; D013007:Growth Hormone-Releasing Hormone; D006801:Humans; D007334:Insulin-Like Growth Factor I; D007945:Leukemia, Lymphoid / Q000532:radiotherapy*; D008297:Male; D010446:Peptide Fragments; D010903:Pituitary Gland, Anterior / Q000528:radiation effects*; D011388:Prolactin / Q000097:blood; D011832:Radiation Injuries / Q000097:blood*; D011879:Radiotherapy Dosage; D013002:Somatomedins / Q000097:blood
chemical_list: D010446:Peptide Fragments; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone