57 LONGITUDINAL STUDY OF GH SECRETION, SOMATOMEDIN AND GROWTH IN THE TWO YEARS FOLLOWING CRANIAL IRRADIATION

Abstract

In order to define characteristics and timing of GH deficiency after cranial irradiation a longitudinal study was performed on 16 children (2 to 15 yr) after > 3000 rads for medulloblastoma (n=9) or other posterior fossa tumors (n=7). At onset (TO), after 1 (T1) and 2 yr (T2) GH secretion was assessed by 1) GH peak response to AITT, 2) sleep GH peak, 3) plasma SmC/IGF I (RIA) and Sm (bioassay) expressed as % of normal values based on age and pubertal standards. At TO and T1 the mean (n=13) GH (AITT) peak values were respectively 21.8 ± 12.2 (SD) and 12.2 ± 5.7 ng/ml (p < 0.02). In 7 cases fully evaluated at T1 and T2 the frequency of GH secretion abnormalities were as shown below (GH, ng/ml). At time T2 3/7 children had complete GH deficiency. The mean SmC/IGF I values at T1 and T2 were respectively 0.54 ± 0.26 and 0.57 ± 0.35 %. Sm by bioassay did not show any clear correlation with RIA. From TO to T2 the mean height loss was 1.21 ± 0.4 SD (- 0.8 to - 1.8 SD) at T2 in this group. In conclusion, this study demonstrated the early occurence of various GH secretory disturbances and growth retardation. It should provide further information on the mechanism of radiation induced GH deficiency and help to define therapeutic strategies (supported by INSERM grant, 1982).