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Growth hormone release in children after cranial irradiation
Insights
Evaluating growth hormone (GH) secretion in children post-brain radiotherapy is crucial. Measuring spontaneous 24-hour GH secretion is recommended over provocative tests like GHRH and AITT for accurate assessment after cranial irradiation.
Area of Science:
- Pediatric Endocrinology
- Neuro-oncology
- Radiotherapy Research
Background:
- Growth hormone (GH) deficiency is a common complication in children following brain radiotherapy.
- Cranial irradiation for brain, eye, or epipharynx tumors can impair GH secretion.
- Accurate assessment of GH secretory capacity is vital for managing growth retardation.
Purpose of the Study:
- To compare different methods for assessing GH secretion in children after cranial radiotherapy.
- To determine the most reliable method for evaluating GH secretory capability in this patient population.
Main Methods:
- Nineteen children who received cranial radiotherapy were studied.
- Growth hormone (GH) levels were measured over a 24-hour period with frequent sampling.
- GH secretion was also assessed using growth hormone-releasing hormone (GHRH) and arginine-insulin tolerance tests (AITT).
Main Results:
- All children exhibited disturbed 24-hour GH profiles with reduced secretion and low-amplitude peaks.
- Hypothalamic damage was indicated by prompt GHRH responses in 16 children.
- GH response to GHRH did not correlate with spontaneous 24-hour secretion; AITT showed individual discrepancies.
Conclusions:
- Spontaneous 24-hour GH secretion measurement is suggested as the most reliable method for evaluating GH secretory capability post-cranial irradiation.
- Provocative tests like GHRH and AITT may be less reliable for assessing GH secretion in children after brain radiotherapy.
- Findings highlight the need for tailored diagnostic approaches in pediatric oncology patients.
Abstract:
Growth retardation due to growth hormone (GH) deficiency is common in children after radiotherapy to the brain. Different methods for assessment of GH secretion were compared in 19 children who had received radiotherapy to the brain as part of treatment for a tumor of the brain, eye or epipharynx. GH was measured over a 24-hour period (72 sampling periods of 20 min each), as well as after administration of growth hormone-releasing hormone (GHRH) and arginine-insulin (AITT) tests. We found the 24-hour GH profile to be disturbed in all children; there was a low overall secretion with few peaks of low amplitude but a diurnal rhythm still discernable. In 16 children a prompt rise in GHRH after GHRH1-40 was seen indicating hypothalamic damage. The GH response after GHRH was not found to be correlated to the spontaneous secretion over 24 h. The results of the AITT showed discrepancies to the 24-hour GH profile in individual cases making this test unreliable in spite of a good overall correlation between the tests. Therefore, we suggest measurement of spontaneous secretion when GH-secretory capability is to be evaluated after cranial irradiation for a brain tumor.