Bone metabolism and circulating IGF-I and IGFBPs in dexamethasone-treated preterm infants.
OBJECTIVE
To characterize the ontogeny of circulating IGF-I, the IGF binding proteins (IGFBPs) and biochemical markers of bone turnover in dexamethasone (DEX)-treated preterm infants with chronic lung disease.


METHODS
Plasma and urine samples from 17 infants were obtained prior to DEX, after 9-12 days of DEX and 10 days after the completion of DEX to assess plasma IGF-I, IGFBPs, osteocalcin and urinary N-telopeptide. Nutrient intakes and growth were monitored from birth until term corrected age at which time body composition was evaluated by dual energy X-ray absorptiometry.


RESULTS
Although nutrient intakes did not differ during or after DEX, weight gain (115 vs. 174 g/week) and length gain (0.7 vs. 1.0 cm/week) were higher after DEX treatment. Plasma IGF-I, IGFBP-3 and osteocalcin increased over time. N-telopeptide was the only biochemical parameter which appeared to be suppressed during DEX (1342 nM bone collagen equivalents/mM creatinine vs. 2486 (pre-DEX) and 2292 (post-DEX)). At term corrected age, bone mineral content was lower in dexamethasone-treated infants compared to preterm and term reference infants.


CONCLUSIONS
Changes in circulating IGFBP-2 and IGFBP-3 paralleled the changes reported in non-steroid-treated infants; however, it remains uncertain whether the natural rise in IGF-I was suppressed by DEX treatment. Assessment of these circulating components provided limited insight into the mechanisms by which DEX alters growth and bone turnover.
Ward
W E
WE
Department of Pediatrics, Children's Hospital, Hamilton Health Sciences Corporation, McMaster University, Ontario, Canada.
Atkinson
S A
SA
Donovan
S M
SM
Paes
B
B
D015502:Absorptiometry, Photon; D001823:Body Composition; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D003094:Collagen / Q000652:urine; D024042:Collagen Type I; D003907:Dexamethasone / Q000627:therapeutic use*; D005260:Female; D005865:Gestational Age; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000378:metabolism*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008895:Milk, Human; D015675:Osteocalcin / Q000097:blood; D010455:Peptides / Q000652:urine
D024042:Collagen Type I; D005938:Glucocorticoids; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone; D003094:Collagen