The insulin-like growth factor-I response to growth hormone is increased in prepubertal children with obesity and tall stature.
BACKGROUND
Children with obesity [body mass index (BMI) > +2 sd score (SDS)] and children with constitutional tall stature [CTS; height > +2 SDS)] have normal-high serum IGF-I levels, associated with a low and broad range of GH secretion, respectively. This suggests increased sensitivity to GH, whereas children with idiopathic short stature (ISS; height < -2 SDS) are believed to have decreased GH sensitivity. OBJECTIVE, DESIGN, AND MAIN OUTCOME MEASURE: To compare the responsiveness to GH in 62 prepubertal children (43 females, 19 males) with obesity, CTS, or ISS and 26 controls (15 females, 11 males; height and BMI -2 to +2 SDS), we used an IGF-I generation test and studied the IGF-I concentration 24 h after a single injection of GH (2 mg/m2).


METHODS
Twenty patients with obesity, 20 with CTS, 22 with ISS, and 26 controls were studied. The mean age was 8.3 +/- 2.9 yr, with no difference in age or gender between groups.


RESULTS
Compared with controls, the mean IGF-I increment was 80% higher in obese children and 36% higher in tall children (P < 0.05 obese or tall vs. control children; P = 0.05 obese vs. tall children). Conversely, the IGF-I increment was similar in short compared with control children, despite a mean baseline IGF-I 62% lower in short children (P < 0.05 vs. controls). In all groups, the IGF-I increment was correlated with the BMI SDS or the fat mass percentage (r = 0.51-0.58, P < 0.05).


CONCLUSIONS
Obese children tend to have greater GH responsiveness than tall children, and both have greater GH responsiveness than controls. GH responsiveness was similar in controls and short children, despite a lower baseline IGF-I in short children. Whether the differences in the IGF-I response to GH between these children reflect differences in the respective anabolic (growth promotion) and metabolic (i.e. insulin action modulation) roles of circulating IGF-I is unknown.
Bouhours-Nouet
Natacha
N
Department of Pediatrics, University Hospital, 4 rue Larrey, 49033 Angers Cedex 01, France.
Gatelais
Frédérique
F
Boux de Casson
Florence
F
Rouleau
Stéphanie
S
Coutant
Régis
R
D001823:Body Composition / Q000502:physiology; D001827:Body Height / Q000502:physiology*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D005260:Female; D006130:Growth Disorders / Q000188:drug therapy / Q000378:metabolism; D019382:Human Growth Hormone / Q000008:administration & dosage / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D009765:Obesity / Q000378:metabolism*
C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I