Bone and fat mass in relation to postnatal levels of insulin-like growth factors in prematurely born children at 4y of age

BACKGROUND: Children born prematurely may be at risk of developing osteopenia. This study investigated whether insulin-like growth factors (IGFs) in the early postnatal period influence bone mass and body composition in prematurely born children. METHODS: A total of 74 control (gestational age >36 wk; n = 37) and preterm (gestational age <32 wk; n = 37) infants were investigated (mean age +/- SD: 4.59 +/- 0.31 y). Bone mineral density, body composition, and markers of bone and mineral metabolism were investigated in relation to postnatal IGF levels. RESULTS: After adjusting for confounders, we found no differences in bone mass, but significantly less lean mass, increased fat mass, and increased osteocalcin levels in ex-preterm infants. Forward stepwise multiple analysis revealed that higher late postnatal IGF-II levels predict lumbar spine bone mineral content (P < 0.05) and lean mass (P < 0.05). When the birth weight standard deviation score was included in the analysis, higher early postnatal IGF-I levels predicted both lumbar spine bone mineral density and bone mineral content (P < 0.05). Higher early postnatal IGF binding protein-3 (P < 0.01) predicted increased fat mass at 4-y follow-up. CONCLUSION: Ex-preterm children have normal bone mass but different body composition compared with full-term controls. Higher early IGF-I and late postnatal IGF-II concentrations are positive predictors of lumbar spine bone mass.