Growth hormone secretion, puberty and adult height after cranial irradiation with 18 Gy for leukaemia

The dose of prophylactic cranial irradiation given to patients for acute lymphoblastic leukaemia has been decreased from 24 to 18 Gy, but the beneficial effect of this decrease on growth is controversial. This study compares the growth hormone (GH) secretion and growth of 35 patients (20 boys) given 18 Gy at 3.7+/-0.3 (SE) years, and routinely evaluated 5.4+/-0.4 years after irradiation to define the indications for GH treatment in these patients. Of these, 63% had a low GH peak (< 10 microg/l) after one (22 cases) or two (17 cases) stimulation tests. The plasma concentrations of insulin-like growth factor I and its GH-dependent binding protein were normal for age in all but two cases. The height changes between irradiation and evaluation were correlated with the GH peaks (P < 0.03) and were concordant, except in patients with early puberty. This occurred in 16 patients including all 12 girls irradiated before 4 years of age. A significant (P < 0.03) reduction in height (SD) between irradiation and adult height occurred in untreated GH-deficient patients (-1+/-0.3, n=6), but not in GH-deficient patients given GH (-0.6+/-0.3, n=8) or in those with normal GH peak (-0.4+/-0.3, n=7). CONCLUSION: In children irradiated for acute lymphoblastic leukaemia, GH deficiency is frequent after 18 Gy but its impact on adult height is smaller than after higher doses. We suggest that the indications for gonadotropin releasing hormone analogue therapy should be broad in patients with early or rapidly progressing puberty and those for GH therapy in those patients with a below average constitutional height before irradiation.