Several parameters of 24-hour GH secretion : maximum peak, integrated concentration (IC) and number of peaks (above 5 ng/ml) were studied in 93 children of varying height : 55 children with growth retardation, 22 of normal height (± 2 SD), and 16 tall children, and correlated with their growth velocity (cm/yr). Sampling for GH measurement was carried out over a 24-hour period, every 30 minutes during the day and every 20 minutes during the night. Growth velocity was calculated in cm/yr for the two preceding years and height in SDS.
The group was composed of 74 boys and 19 girls. Mean chronological age was 10 yrs 6 months. Growth velocity was 4.7 cm/yr for the group as a whole, 3.9 cm/yr for the children with growth retardation, 4.6 cm/yr for the normal children and 7.4 cm/yr for the tall children. Study of 24-hour GH secretion for the group as a whole gave the following results : maximum peak 22.4 ± 13.4 ng/ml, number of peaks 4.6 ± 1.9 and IC 3.5 ± 2 ng/ml. The multiple regression test showed a significant correlation (p 0,001) between growth velocity and the number of peaks during the night and over the 24-hour period. This correlation also existed in all three groups but was stronger in the normal children than in the other two groups. However, no correlation was found between growth velocity, value of the maximum peak and integrated concentration in the group as a whole nor in three groups.
In conclusion, the pulsatile nature of GH secretion is the factor with the closest correlation with growth velocity, in children with growth retardation as well as in children of normal height and tall children; on the other hand, there is no significant correlation with maximum peak and 24-hour integrated concentration.