title: SERUM INSULIN-LIKE GROWTH FACTOR 1 IN LEBANESE SCHOOLCHILDREN AND ITS RELATION TO VITAMIN D AND FERRITIN LEVELS.
abstract: OBJECTIVE
  The aims of our study were to establish reference values for insulin-like growth factor 1 (IGF-1) in Lebanese schoolchildren and to evaluate the relationship between IGF-1 and age, sex, body mass index (BMI), vitamin D, and ferritin.
  
  
  METHODS
  This cross-sectional study included 952 Lebanese schoolchildren (495 boys and 457 girls) aged 8 to 18 years. Blood samples were taken from children attending 10 schools with different socio-economic status (SES). Chemiluminescent immunoassays were used for IGF-1, 25 hydroxyvitamin D (25(OH)D), testosterone, and ferritin measurements.
  
  
  RESULTS
  The mean age was 13.46 ± 2.80 with no significant difference according to sex. IGF-1 was correlated with age in both sexes (P<.0001); it was higher in girls compared to boys (P = .007) and peaked at the ages of 14 and 12 for boys and girls, respectively. For each age group, the median IGF-1 value was higher compared to the values provided by the kit. IGF-1 was significantly correlated with BMI in boys (r = 0.16, P<.0001) but not girls. In both sexes, IGF-1 was inversely correlated with 25(OH)D and ferritin values. After adjustment for age, BMI, and height, the correlation between IGF-1 and 25(OH)D disappeared, whereas the relationship with ferritin persisted (P<.001 for boys, P = .002 for girls). For both sexes, multivariate regression analysis revealed independent associations between IGF-1 and height, Tanner stage, and ferritin. An association was also noted in boys for BMI and testosterone.
  
  
  CONCLUSIONS
  Our results showed higher and earlier peak IGF-1 values in the pediatric Lebanese population compared to western populations. In addition, an independent inverse relationship was observed between IGF-1 and ferritin. Further studies are needed to identify the reason(s) underlying these results.
  
  
  BACKGROUND
  BMI = body mass index CRP = C-reactive protein CV = coefficient of variation GH = growth hormone IGF-1 = insulin-like growth factor 1 25(OH)D = 25 hydroxyvitamin D SES = socio-economic status TSH = thyroid-stimulating hormone.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Gannagé-Yared
authors.forename: Elise
authors.initials: E
authors.lastname: Chahine
authors.forename: Vanessa
authors.initials: V
authors.lastname: Farah
authors.forename: Tony
authors.initials: T
authors.lastname: Ibrahim
authors.forename: Nadia
authors.initials: N
authors.lastname: Asmar
authors.forename: Georges
authors.initials: G
authors.lastname: Halaby
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005293:Ferritins / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007861:Lebanon / Q000453:epidemiology; D008297:Male; D012574:Schools / Q000706:statistics & numerical data; D012737:Sex Factors; D013334:Students / Q000706:statistics & numerical data; D014807:Vitamin D / Q000097:blood*
chemical_list: D014807:Vitamin D; D007334:Insulin-Like Growth Factor I; D005293:Ferritins