Is insulin-like growth factor-1 monitoring useful in assessing the response to growth hormone of growth hormone-deficient children?

OBJECTIVE

To assess the relationship between insulin-like growth factor-1 (IGF-1), the growth hormone (GH) dose utilized to treat GH-deficient children and the changes noticed in height-standard deviation score (H-SDS) and height velocity (HV).

STUDY DESIGN

We studied 24 prepubertal GH-deficient patients with a mean age of 10.5 +/- 1.8 years and a mean bone age (BA) of 8.4 +/- 2.1 years. H-SDS for chronologic age (CA) and BA before therapy were -2.6 +/- 0.8 and -1.2 +/- 0.8, whereas height velocity (HV)-SDS was -1.1 +/- 1.5. Serum IGF-1 and insulin-like growth factor binding protein-3 (IGFBP-3) levels were measured before, after 6 and 12 months of GH, and correlated with the GH dose used. Based on the increment of IGF-1 used during treatment, patients were divided into 2 groups: G1 (>1 SDS) and G2 (<1 SDS). HV-SDS and interval height increases were analyzed.

RESULTS

HV-SDS, as well as H-SDS for CA and BA during the first year of treatment, were significantly greater than before therapy. IGF-1 SDS increased significantly during the first 6 months of therapy (P <.0003), but increased no further at 12 months despite the use of a higher GH dose (0.1 vs 0.14 IU/kg/day), whereas IGFBP-3 SDS increased at both 6 and 12 months. There was no correlation between the GH dose used and IGF-1 and IGFBP-3 levels. When patients were divided according to their IGF-1 increment during therapy, a significant increase in H-SDS for BA and in HV-SDS was noted only in group 2.

CONCLUSIONS

The increment in IGF-1 SDS during therapy did not correlate with the interval height increase. IGF-1 measurement may be helpful in monitoring compliance and safety, but seems to be less useful in adjusting the GH dose needed to treat prepubertal GH-deficient children.