Serum insulin/like growth factor I, bone mineral density and biochemical markers of bone metabolism in children with idiopathic osteoporosis.
OBJECTIVE
To determine whether the serum concentration of insulin-like growth factor I (IGF-I) correlates with the occurrence of idiopathic osteoporosis in children, and whether serum levels of IGF-I correlate with selected bone metabolism markers in patients with osteoporosis.


METHODS
The study comprised 24 patients aged 7-18 years, including 12 with idiopathic osteoporosis and 12 control children. Bone mineralisation disorders were diagnosed on the basis of complex clinical, densitometric and biochemical evaluation. In all children serum concentration of IGF-I was estimated by radioimmunoassay and the third fraction of IGF binding proteins (IGFBP3) by immunoradiometry. In children with osteoporosis the indices of bone metabolism were also assessed, e.g. serum levels of osteocalcin and activity of bone isoenzyme of alkaline phosphatase (bone formation markers) and urine concentration of pyridinoline and deoxypyridinoline and collagen type I crosslinked C-telopeptyde (resorption markers).


RESULTS
It was found that in children with osteoporosis IGF-I concentration was significantly lower than in the control group (mean values were 583 and 850 ng/ml, respectively; P<0.05). These differences were independent on biological age of the studied children and were present in all adolescence stages. Concentrations of IGFBP3 did not differ significantly between groups (3593 vs. 3955 ng/ml), while that of IFG-I correlated positively with total and spinal bone mineral density (R=0.85 and R=0.80, respectively; P<0.00001). In children with osteoporosis there was also a significant relationship between IGF-I concentration and elimination of pyridinoline and deoxypyridinoline with urine (R=0.64 and R=0.65, respectively; P<0.05). There was no significant correlation between the concentration of IGF-I and IGFBP3 and other studied bone metabolism markers.


CONCLUSIONS
The conducted study revealed that lower IFG-I concentrations correlate with higher bone resorption markers values and decreased mineralisation. These results suggest the importance of insulin-like growth factor in the ethiopathogenesis of idiopathic osteoporosis, which needs to be confirmed in further studies.
Chlebna-Sokol
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Department of Paediatric Propedeutics, Institute of Paediatry, Medical University of Lodz, 91-738, Lodz, Poland.
Rusinska
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A
D000293:Adolescent; D000469:Alkaline Phosphatase / Q000097:blood; D000596:Amino Acids / Q000652:urine; D015415:Biomarkers / Q000032:analysis; D015992:Body Mass Index; D015519:Bone Density; D001842:Bone and Bones / Q000201:enzymology / Q000378:metabolism*; D002648:Child; D003094:Collagen / Q000652:urine; D024042:Collagen Type I; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007527:Isoenzymes / Q000097:blood; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000097:blood / Q000378:metabolism*; D010455:Peptides / Q000652:urine
D000596:Amino Acids; D015415:Biomarkers; D024042:Collagen Type I; D018972:Insulin-Like Growth Factor Binding Protein 3; D007527:Isoenzymes; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; C015484:pyridinoline; D007334:Insulin-Like Growth Factor I; C036020:deoxypyridinoline; D003094:Collagen; D000469:Alkaline Phosphatase