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Elevated growth hormone secretory rate in premature infants: deconvolution analysis of pulsatile growth hormone
N M Wright1, F J Northington, J D Miller
1Department of Pediatrics, University of Virginia Health Sciences Center, Charlottesville 22908.
Insights
Premature infants exhibit significantly higher growth hormone (GH) secretory burst amplitudes and production rates compared to term infants. This study utilized frequent blood sampling and deconvolution analysis to reveal these distinct GH profiles in neonates.
Area of Science:
- Neonatal physiology
- Endocrinology
- Growth hormone research
Background:
- Premature infants display elevated circulating growth hormone (GH) concentrations compared to term infants.
- Previous studies used less frequent sampling (30-min intervals) and pulse detection algorithms to analyze GH patterns.
Purpose of the Study:
- To investigate differences in GH secretory rates and half-life (t1/2) between premature and term infants.
- To employ high-frequency blood sampling and deconvolution analysis for precise GH parameter estimation.
Main Methods:
- Collected blood samples every 15 minutes for 6 hours from 11 neonates (5 premature, 6 term).
- Utilized indwelling arterial catheters for serial blood draws.
- Measured GH concentrations using radioimmunoassay (RIA) and applied deconvolution analysis to estimate secretory and clearance parameters.
Main Results:
- Premature infants showed significantly higher GH secretory burst amplitudes (2.2 vs. 1.4 µg/L/min, p=0.02).
- Production rates were markedly elevated in premature infants (811 vs. 283 µg/L/6h, p=0.03).
- GH mass per secretory burst was also higher in premature infants (106 vs. 38 µg/L, p=0.049).
Conclusions:
- Premature infants possess distinct GH secretory dynamics, characterized by larger and more frequent secretory bursts.
- These findings highlight significant differences in GH regulation between premature and term neonates.
Abstract:
Premature infants have higher circulating concentrations of growth hormone (GH) than term infants. Previous investigations of these differences have used sampling frequencies of every 30 min with subsequent application of pulse detection algorithms, such as the CLUSTER program, to assess serum GH pulse parameters. To determine differences in GH secretory rates or GH t1/2 values between premature and term infants, we have sampled 11 neonates at 15-min intervals. We performed deconvolution analysis of the resultant plasma GH values to estimate GH secretory and clearance parameters. Five premature infants (gestational age range 24-34 wk) and six term infants (gestational age range 38-42 wk) were sampled every 15 min for 6 h. All subjects had indwelling arterial catheters. GH was measured (in duplicate) by RIA using 10 microL of plasma. Premature infants had higher secretory burst amplitudes (2.2 +/- 0.13 micrograms/L/min versus 1.4 +/- 0.27 micrograms/L/min, p = 0.02), higher production rates (product of the total number of bursts and the mean mass of GH secreted per burst, 811 +/- 173 micrograms/L/6 h versus 283 +/- 77 micrograms/L/6 h, p = 0.03), and a higher mass of GH per secretory burst (106 +/- 25 micrograms/L versus 38 +/- 11 micrograms/L, p = 0.049) than term infants. The integrated plasma GH concentration exhibited a strong trend toward a higher value in the premature infants (18,100 +/- 800 micrograms/L versus 10,200 +/- 2,700 micrograms/L, p = 0.067).(ABSTRACT TRUNCATED AT 250 WORDS)