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The effects of cranial irradiation on growth hormone secretion
Insights
Children treated with cranial irradiation exhibit impaired growth hormone (GH) secretion, with significantly reduced 24-hour GH output and blunted responses to standard stimulation tests. This highlights potential long-term endocrine effects of radiation therapy in pediatric patients.
Area of Science:
- Pediatric Endocrinology
- Radiation Oncology
- Endocrinology
Background:
- Cranial irradiation in childhood can impact endocrine function.
- Growth hormone (GH) deficiency is a potential consequence.
- Assessing GH secretion in these patients requires careful evaluation.
Purpose of the Study:
- To evaluate growth hormone (GH) secretion in children previously treated with cranial irradiation.
- To compare GH response to pharmacological stimuli and physiological secretion with normal controls.
- To assess the adequacy of standard GH stimulation tests in this population.
Main Methods:
- Studied 14 children with prior cranial irradiation (2-14 years earlier).
- Administered insulin hypoglycemia test (ITT) and arginine stimulation test.
- Measured integrated GH concentrations over 24 hours using continuous blood sampling.
- Compared results with a control group of 5 healthy children.
Main Results:
- All 14 children showed a blunted GH response to ITT.
- Twelve children had subnormal GH response to arginine.
- Irradiated patients had significantly reduced mean integrated GH concentration (2.2 vs. 8.8 mU/l) and total 24-hour GH output (105.7 vs. 391.7 mU).
- Reduced GH output was also observed during the first six hours of sleep.
Conclusions:
- Cranial irradiation significantly impairs both stimulated and physiological GH secretion in children.
- Standard GH stimulation tests may underestimate GH deficiency in irradiated patients.
- Comprehensive assessment including 24-hour GH profiling is crucial for accurate diagnosis.
Abstract:
Growth hormone (GH) secretion has been studied under physiological conditions and in response to standard pharmacological stimuli in 14 children, who had previously received cranial irradiation between two and fourteen years earlier. All fourteen showed a blunted GH response to insulin hypoglycaemia and, in twelve, the GH response to arginine stimulation was also subnormal. Physiological GH secretion was studied by measuring integrated GH concentrations in 30 min blood samples collected over a 24 hour period by a continuous withdrawal pump. Compared to normal controls (n = 5), the irradiated patients showed a significant reduction in the mean integrated GH concentration (2.2: 8.8 mU/l; p less than 0.002), the total 24 hour GH output (mean 105.7 mU vs. 391.7 mU; p less than 0.002) and the mean GH output during the first six hours of sleep (mean 48.2 mU vs. 226 mU; p less than 0.002). There was no significant correlation between the maximum peak GH response to either pharmacological test and the total 24 hour GH output. Conventionally most short children undergo two provocative tests of GH release and if the GH response to one of the two tests is normal, it is usually assumed that GH production is adequate. Adopting these criteria in this study it would have been assumed incorrectly that GH production was normal in two children. Nonetheless all 14 children showed a blunted GH response to an ITT as well as a reduced total 24 hour GH output.(ABSTRACT TRUNCATED AT 250 WORDS)