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Irradiation of the head. Immediate effect on growth hormone secretion in children
Insights
Cranial irradiation may suppress growth hormone (GH) in children with leukemia. This study found lower GH levels and peak responses after irradiation, suggesting a direct impact on the hypothalamic pituitary axis.
Area of Science:
- Pediatric Endocrinology
- Neuro-oncology
- Radiation Oncology
Background:
- Leukemic children often receive prophylactic cranial irradiation.
- Assessing pituitary function is crucial in these patients.
- Normal hypothalamic-pituitary axis function is assumed prior to treatment.
Purpose of the Study:
- To evaluate the effect of prophylactic cranial irradiation on plasma growth hormone (GH) levels.
- To determine if cranial irradiation impacts the hypothalamic-pituitary axis in leukemic children.
- To assess changes in GH secretion patterns before and after irradiation.
Main Methods:
- Hourly plasma GH sampling from 1000 h to 0700 h in 10 leukemic children.
- Measurements were taken before and after a 3-week course of cranial irradiation.
- Comparison of GH levels with endocrinologically normal children.
Main Results:
- Mean GH levels before irradiation were comparable to normal controls, indicating normal pituitary function.
- Post-irradiation GH levels were generally lower than pre-irradiation levels.
- A statistically significant decrease in GH was observed at 0100 h, and peak GH responses were reduced (p < 0.02).
Conclusions:
- Prophylactic cranial irradiation appears to have an immediate suppressive effect on the hypothalamic-pituitary axis.
- The findings suggest that even in the absence of CNS involvement, irradiation can impact GH secretion.
- Further investigation into long-term endocrine effects is warranted.
Abstract:
Plasma growth hormone (GH) was determined in samples obtained hourly from 1000 h to 0700 h before, and after a 3 week course of "prophylactic" cranial irradiation, in ten leukemic children who had no clinical or laboratory evidence of central nervous system involvement. The mean per hour value of GH prior to irradiation (4.1 +/- 2.4 ng/ml) was similar to that of 7 endocrinologically normal children (4.09 +/- 2.4 ng/ml), a finding strongly suggesting normal pituitary function prior to irradiation. Following irradiation GH levels at each hour were, in general, lower than before. The difference is statistically significant at 0100 h. The peak GH responses were lower following than preceeding irradiation (p less than 0.02). The findings suggest an immediate suppressive effect of irradiadiation on the apparently normal hypothalamic pituitary axis in children.