Background: It has been reported that short-term increases of the bone formation markers intact amino-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BALP) and osteocalcin display different temporal patterns. In adults, the biphasic model of GH action in bone remodelling shows that GH treatment results initially in an increased bone resorption with a concomitant bone loss, which later on is followed by increased bone formation. In children, little is known how bone remodelling takes place.
Objective and hypotheses: Bone formation markers reflect different events during osteogenesis, and respond with different time courses during anabolic GH treatment.
Method: The study population comprised 128 short prepubertal children (age range 3−11 years; 90 boys, 38 girls) who participated in a longitudinal, prospective, multicenter study in individual GH dosing1, TRN 98-0198-003. The investigated children had either normal or reduced levels of GH secretion. Data from the first 2 years of GH treatment were analyzed. The bone markers were measured using the IDS-iSYS automatic system (immunodiagnostic systems)2. The DXA derived variable bone mineral density (BMD) was measured by Lunar DPX-L or Lunar Prodigy.
Results: The bone markers PINP, BALP, osteocalcin and 25-hydroxyvitamin D (25(OH) D) at start and deltaPINP at 3 months of GH treatment explained 63% of the growth response at 2 years (P<0.0001), while only 26% of the variation in BMD response after 2 years of treatment was explained (P<0.0001).
Conclusion: Bone markers at start of GH treatment, and the 3 months increase of PINP were associated with both growth response and bone mineralization after 2 years of treatment, but with different magnitude of impact on these anabolic GH effects.