Abstract
We have performed a mixed longitudinal study of 59 spontaneous (24hr profiles) and stimulated (insulin-induced hypoglycaemia tests - ITT) measures of growth hormone (GH) secretion in 35 prepubertal children aged 1.5 to 11.2 years with BT distant from the hypothalamo-pituitary area before and at 6-12 monthly intervals up to 3 years after surgery ± radiotherapy ± chemotherapy. We have compared results with those obtained in 26 short normal controls (SN). The profiles were analysed by a distribution method. We observed discrepancies between peaks of spontaneous and stimulated GH in BT but not SN. The ratio was significantly greater in all BT groups compared to SN (p<0.05). Peak GH to ITT was not influenced either by the degree of hypoglycaemia (r=0.1, p = 0.65) nor by days off dexamethasone therapy in those children assessed before radiotherapy (r = 0.24, p = 0.37). In 14 BT children in whom GHRH tests at 2 doses (1 μg/kg and 0.1 μg/kg) were performed, correlation with spontaneous peaks was greater with the low dose (r=0.7, p=0.005) than the high dose (r=0.27, p=0.26). A spontaneous/stimulated ratio approaching 1.0 suggests intact hypothalamic GHRH and somatostatin (SS) tone. ITT results reflect SS tone which was abnormal in children with BT. 24hr profile results reflect GHRH secretion and low dose GHRH tests identified this.
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