CATCH-UP GROWTH IS INTRINSIC TO THE EPIPHYSEAL GROWTH PLATE

Catch-up growth is believed to result from a central nervous system mechanism that compares actual growth to a set point and adjusts growth velocity accordingly. Alternatively, we hypothesized that catch-up growth is intrinsic to the growth plate. To test this hypothesis, we infused dexamethasone phosphate for 4 weeks directly into one proximal tibial growth plate of 5-week old rabbits and infused vehicle into the contralateral growth plate. Growth velocity at each tibial growth plate was determined radiographically. Dexamethasone decreased the growth velocity of the treated growth plate by 37 ± 8 % (mean ± SEM, p < 0.01) compared to the control, causing a growth deficit of 4.8 ± 1.2 mm (p<0.01). After the end of the infusion, the growth velocity of the dexamethasone-treated growth plate rebounded above that of the control and ultimately corrected 52 ± 10 % of the deficit (p<0.01). Because the catch-up growth occurred solely within the dexamethasone-treated growth plate, we conclude that catch-up growth is intrinsic to the epiphyseal growth plate and cannot be explained by a systemic mechanism.