Endocrine Abstracts

Background: IGF1 is the biochemical marker of growth as it is supposed to reflect the activity of the GH axis. The usefulness of IGF1 measurements in children under 3 years has not been verified to date.

Aim: We analysed the relationship between serum IGF1 concentration and growth velocity (GV) in children under the age of 3 years.

Methods: We compared 300 IGF1 concentrations taken in children younger than 3 years with their GV at time of collection. We included patients with different diagnoses; patients on GH therapy were excluded.

Three groups of patients were identified according to GV: group A GV-SDS>−0.8, group B GV-SDS<−2, group C −0.8>GV-SDS>−2.

Results: Group A (n=185): despite the normal GV, IGF1 was less than the lower limit of the normal range in 50.3% of patients, this being more frequent (65.5%) in the first year of life than in the second (41.2%) or the third (40%).

Group B (n=58): IGF1 was appropriately low in 74.1% of patients but within the normal range in 25.9% of these patients with poor GV.

Group C (n=57): in 71.9% of patients, the IGF1 was low. In the remaining patients, the concentration was within the first quartile of the range in 87.5% of cases.

A total of 120 patients with low IGF1 were formally tested for GH deficiency (GHD) (glucagon stimulation) and 93 of them were GHD (IGF1 specificity 77.5%).

BMI-SDS was equally distributed between the three groups and the quartiles of IGF1, therefore excluding an impact of nutrition on IGF1 concentrations.

Conclusions: These preliminary data suggest that the relationship between IGF1 concentration and GV before 3 years of age is poor. This is even more evident in patients with normal GV, and especially in the youngest ones (<1 year). In this cohort of patients specificity of IGF1, as a preliminary diagnostic test GHD, is 77.5%.