COMPARISON OF THE INTRAVENOUS GHRH TEST AND 24-HOUR HORMONE SECRETION IN CHILDREN WITH GROWTH RETARDATION

Abstract

A stimulatory test with intravenous GHRH (2mcg/kg) and study of physiological GH secretion over the 24-hour period with GH sampling every 20 min (calculation of the integrated concentration (IC) and the value of the maximum nocturnal peak) was carried out in 94 children. Their mean age was 10.75±3.35yr and mean growth retardation -2.78±0.67 SD. The means of the parameters studied were : GH peak after GHRH 30.4±16.8, ng/ml, IC 3.11±1.97ng/ml/min and physiological secretory peak 26±4ng/ml. The children were divided into three subgroups according to their IC : normal IC (Gl,m=4;67±2.2ng/ml/min, n=39), intermediate (G2, m=2.36±0.3ng/ml/min, n=30) and low (G3,m=1.65±0.45ng/ml/min, n=25). The mean of GH peaks after GHRH did not significantly differ between the three subgroups. The means were respectively : G1,32.97±2.71 ng/ml; G2,30.39±2.9 ng/ml; and G3,26.25±3.61 ng/ml. There was no significant correlation between the GH peak after GHRH on the one hand and the IC or the physiological secretory peak on the other in these three groups. The GHRH test was considered positive when the GH peak was greater than 10 ng/ml. 77 of 94 children had a positive response. 17 children did not respond to GHRH stimulation. Study of the physiological secretion showed GH deficiency in 6 of the 17 children (mean IC 1.45±0.28), but in 11 children 24-hour secretion was normal. The GHRH test does not therefore make it possible to differentiate in testing for pituitary deficiency and cannot be considered as a diagnotic test for GH deficiency.

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