OBJECTIVETo explore the dynamic change in biochemical markers of bone turnover in preterm infants and the effect of early parenteral calcium supply.

METHODSForty preterm infants were divided into parenteral calcium supply group and control group. Blood and urine samples were collected at 24 h and 11 d after birth. Serum osteocalcin (OC) was measured with ELISA, serum carboxyterminal telopeptide type I collagen (ICTP) with radioimmunoassay, serum alkaline phosphatase (AKP), calcium, phosphate, and urine calcium, phosphate, creatinine with automatic biochemical analyzer. Blood samples were also collected from 22 term infants as control. Calcium gluconate (10%, 4 ml/kg x d(-1)) was administered intravenously in parenteral calcium supply group.

RESULTAt 24 h, serum AKP, ICTP [(147.86+/- 44.87)IU, (57.36+/- 6.34)micro g/L] in preterm infants were significantly higher than those [(147.86+/- 44.87)IU, (57.36+/- 6.34)micro g/L] in term infants, and negatively correlated with gestational age and birth weight (r =-0.528, P<0.01; -0.614, P< 0.01), but serum OC [(648.77+/- 238.89) nmol/L] in preterm infants was lower than that [(851.68+/- 238.69)nmol/L] of term infants, and positively correlated with gestational age and birth weight (r=0.359, P< 0.05; 0.376, P< 0.01). At 11 day, serum OC [947.25+/- 335.47)nmol/L] in preterm infants was markedly elevated and reached the level of term infants [(941.65+/- 297.28)nmol/L], but serum ICTP [(65.44+/- 6.24)micro g/L] in preterm infants was higher than that [(57.10+/- 3.48)micro g/L] in term infants all along. Serum AKP [(246.00+/-66.64)IU] in parenteral calcium supply group was higher than that [(206.53+/- 53.9)IU] in the control group. There were no significantly differences in serum OC and ICTP between parenteral calcium supply group and the control group. Calcium in serum and urine was elevated, phosphate in serum and urine was reduced in the parenteral calcium supply group. Urine analysis and kidney ultrasounds were normal.

CONCLUSIONThere is active bone formation and bone resorption in preterms as compared with terms. Alone parenteral calcium supply during early life can not increase formation of bone protein or decrease degradation of bone collagen, but can elevate serum calcium and urine calcium levels. Hematuria and renal calcification were not found in short duration.