Bone turnover markers and bone strength during the first weeks of life in very low birth weight premature infants

Abstract

Objective: To determine the association between changes in bone turnover markers and bone strength of very low birth weight infants during the first eight postnatal weeks. Study design: Twelve very low birth weight premature infants [mean gestational age: 28.4+-0.6 weeks, mean birth weight: 1131+-62 grams] participated in the study. Bone strength was evaluated weekly by quantitative ultrasound measurements of tibial bone speed of sound (SOS, Sunlight Omnisense™). Bone specific alkaline phosphatase (BSAP), a marker of bone formation, and carboxy terminal cross-links telopeptide of type-I collagen (ICTP), a marker of bone resorption, were collected at the ages of one, four and eight weeks. Results: BSAP increased significantly (from 119.9+-16.2 U/L to 132.1+-11.9 U/L and 152.1+-15.7 U/L at one, four and eight weeks of life, respectively, p<0.05). ICTP decreased significantly during the study period (from 122.3+-8.7 ng/ml to 96.0+-4.8 ng/ml and 92.3+-5.4 ng/ml at one, four and eight weeks of life, respectively; p<0.05). There was a significant decrease in bone SOS (from 2886+-29 m/sec to 2792+-30 m/sec and 2753+-30 m/sec at birth, four weeks and eight weeks of life, respectively; p<0.02). There was no correlation between the levels of bone markers and bone SOS. Conclusion: In VLBW premature infants, there is a significant decrease in bone strength concomitant with biochemical evidence for new bone formation (increase in BSAP and a decrease in ICTP) during the first eight postnatal weeks. Changes in the biochemical markers could not predict the changes in bone strength.