The evaluation of 24-hour spontaneous GH secretion in short children: relationship between mean concentration and...

In 116 short children (height < -1.6 SDs), the authors examined GH secretion over 24 hours, by taking blood samples every 20 min and performing an electroencephalographic sleep control. The following GH parameters were evaluated: 24-h mean GH concentration (MGHC); maximum GH peak during the initial cycle of sleep (iMGHP), the nocturnal 12 h (nMGHP) or diurnal 12 h (dMGHP), the number of GH pulses over 24 h (NP), or nocturnal 12 h (nNP) or diurnal 12 h (dNP), the mean pulse amplitude over 24 h (MPA), or nocturnal 12 h (nMPA) or diurnal 12 h (dMPA). The subjects were divided into 3 groups: group 1, 12 subjects with low responses to provocative tests and MGHC < 3 ng/ml; group 2, 36 subjects with normal responses to provocative tests and MGHC < 3 ng/ml; group 3, 68 subjects with MGHC > 3 ng/ml. MGHC was highly correlated (p < 0.001) with iMGHP (r = 0.80), nMGHP (r = 0.82), dMGHP (r = 0.59), MPA (r = 0.85), nMPA (r = 0.86), dMPA (r = 0.56), NP (r = 0.70), nNP (r = 0.68), dNP (r = 0.46). By the analysis of the regression equations, the values corresponding to 3 ng/ml for MGHC were 11.08 ng/ml for iMGHP, 11.66 ng/ml for nMGHP, 5.21 ng/ml for dMGHP, 7.29 ng/ml for MPA, 8.40 ng/ml for nMPA, 4.25 ng/ml for dMPA, 3.2 for NP, 2.41 for nNP and 0.78 for dNP. By using these values as cut-off points, the diagnostic accuracy yielded 83.6% for iMGHP, 84.5% for nMGHP, 69.8% for dMGHP, 92.2% for MPA, 90.5% for nMPA, 81.9% for dMPA, 80.2% for NP, 77.6% for nNP, 71.5% for dNP. In conclusion, we found a strong correlation between mean GH secretion over 24 h and the number or amplitude of pulses: particularly, nocturnal pulsatile GH parameters show a higher correlation in comparison with diurnal pulsatile GH parameters, so that the examination of GH values during nocturnal hours may be considered a reliable index of GH secretory status.