ESPE Abstracts

Background: The diagnosis of GHD in children is based on auxological, biochemical, neuro-radiological, and genetic tests. Biochemical tests include evaluation of stimulated GH secretion and baseline IGF-1 determination. Although IGF-1 is the most reliable indicator of GH action, its value should always be interpreted in conjunction with other clinical and biochemical parameters. Since IGF-1 has good specificity (about 90%), but low sensitivity (about 70%), normal levels do not always rule out GHD. Our recent studies have shown that the best IGF-1 cut-off for discriminating patients with GHD from healthy subjects is −1.5 SDS. The aim of our research was to evaluate GH secretion and clinical features in short stature patients subdivided in 4 groups according to their serum IGF-1 levels at diagnosis.

Patients and method: 514 short patients (height-SDS (HT-SDS) -2,56 (-5,20; 0,42), age 10,20 (2,00; 17,70)y, 308 boys), were included in this analysis. In all patients median IGF-1 SDS was - 1,13(-6,07; 3,50) and median GH peak (after two stimulation tests (arginine, clonidine, or insulin tolerance test)) was 11,80 μg/L (0,41; 53,00). 6,23% had a GH peak <5 μg/L, 14,79% between 5-8 μg/L, 13,81% between 8-10 μg/L and 65,18% >10 μg/L. Patients were divided into four groups according to their IGF-1 values: group 1 IGF-1<-1,5 (n= 189), group 2 -1,5<IGF-1<1 (n= 83), group 3 -1<IGF-1<0 (n= 154), group 4 IGF-1> 0 (n= 86). Data are presented as median (range). To remove confounding factors, such as BMI and pubertal status, and highlight the correlation between GH peak and IGF-1, we performed a multinomial logistic regression.

Results: BMI-SDS and HT-SDS were lower in patients with higher IGF-1 (P= 0,006) and (P=0,0036). The percentage of patients with GH peak below 5 decreases as the IGF-1 value increases: in group 1 12,70% of patients had a GH peak <5 μg/L, group 2 4,82%, group 3 1,95% and group 4 1,16% (P<0,0001). No differences were observed in patients with GH peak between 5-8 μg/L. Multinomial logistic regression showed that a low IGF-1 level increases the probability of a GH peak <5 μg/L, whereas higher IGF-1 concentrations decrease the likelihood of GHD.

Conclusions: Despite the reported low specificity of IGF-1 measurement in the diagnosis of GHD, we have shown in this study that children with baseline IGF -1>0 are at very low risk of GHD.