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Growth hormone release during sleep in growth-retarded children with normal response to pharmacological tests
Insights
Monitoring nocturnal growth hormone (GH) secretion is crucial for accurately assessing physiological peaks in children with small stature. This study highlights potential discrepancies between pharmacological and sleep-monitoring tests for GH deficiency diagnosis.
Area of Science:
- Pediatric Endocrinology
- Sleep Medicine
- Growth Hormone Physiology
Background:
- Children with small stature and growth rates below 4.5 cm/year require thorough evaluation for growth hormone (GH) deficiency.
- Pharmacological tests (arginine and L-dopa) are commonly used to assess GH release.
- Understanding physiological GH secretion patterns during sleep is essential for accurate diagnosis.
Purpose of the Study:
- To investigate the pattern of physiological growth hormone (GH) secretion during different sleep stages in prepubertal children with small stature.
- To compare the results of pharmacological GH stimulation tests with nocturnal sleep monitoring.
- To evaluate the diagnostic utility of sleep monitoring for GH secretion.
Main Methods:
- Studied 21 prepubertal children (10 boys, 11 girls) with height below the 3rd percentile and slow growth rates.
- Administered arginine and L-dopa stimulation tests to assess GH release.
- Monitored nocturnal sleep stages (1-4 and REM) using electroencephalogram and electro-oculogram.
- Recorded GH levels throughout the night to identify secretory peaks.
Main Results:
- All children showed a GH response >8 ng/ml in at least one pharmacological test, ruling out GH deficiency.
- All 21 children exhibited at least one physiological GH secretory peak >8 ng/ml during sleep.
- Nearly half (48%) of the 46 recorded GH peaks occurred during deep slow-wave sleep (stages 3-4).
- Four patients (19%) had no GH peaks during deep sleep, despite peaks occurring at other times.
Conclusions:
- Nocturnal monitoring of GH secretion is essential for definitively identifying physiological secretory peaks.
- Discrepancies between pharmacological and physiological GH testing can occur.
- Sleep monitoring for GH secretion may serve as a safer alternative to the insulin tolerance test in certain pediatric cases.
Abstract:
Twenty-one prepubertal children of small stature, 10 boys and 11 girls, aged from 4-3 to 12-8 years, were studied. Their height was less than 3rd centile, and during the preceding year all had a growth rate less than 4-5 cm/year. Arginine and L-dopa tests were given, and the release of growth hormone (GH) during monitored sleep was investigated. On the basis of the electroencephalogram and horizontal electro-oculogram, sleep was divided into stages 1-2-3-4 and rapid-eye-movement. All the children had a GH response greater than 8 ng/ml in at least one of the two pharmacological tests, and were therefore accepted as not suffering from GH deficiency. In all 21 children during sleep there was at least one secretory peak with GH greater than 8 ng/ml. Of a total of 46 secretory peaks recorded, 22 (48%) took place during deep, slow sleep (stages 3-4), 10 (22%) during light sleep (stage 2), 10 (22%) during REM sleep, and 4 (8%) during wakening. In 4 patients (19%) no secretory peak was observed during stages 3-4, even though there were peaks at other times. The data (a) show that it is essential to monitor GH throughout the night to ascertain with certainty the presence or absence of physiological secretory peaks of GH; (b) emphasise the rare disagreement between pharmacological and physiological tests; (c) suggest the use of this physiological test for GH secretion in those cases where the insulin test may be hazardous.