Abstract
Although supplementation with growth hormone (GH) is an accepted treatment for children who are GHโdeficient or very small in stature, its effect on the craniofacial skeleton has been little studied. The goal of this study was to compare the absolute and relative growth of the craniofacial skeleton in GHโdeficient dwarf rats to that in wildโtype rats of the same strain, using a mixedโlongitudinal radiographic design. Lateral and dorsoventral Xโrays of the head and hindlimb were obtained weekly in dwarf and wildโtype female Lewis rats from 4 to 9 weeks of age (n = 14 for each time interval). The Xโrays were scanned, 27 cephalometric points were digitized, and selected linear distances were measured between points. Multilevel statistical procedures were used to model growth changes in different regions of the head. Among craniofacial measures, growth curves of the two groups differed greatly in the magnitude of initial size differences and the effect of GH deficiency on growth velocity. Considerable variation (65โ97%) also existed among craniofacial measures with regard to relative maturity (i.e., the percentage of growth completed between the first and last time intervals). The deficiency effect (a quantitative estimate of the extent to which growth velocity was affected by GH) was negatively correlated (r = โ0.52, P < 0.01) with relative maturity of a particular measure. The dependence of the GH effect on relative maturity suggests that different craniofacial morphologies may result depending on the timing of GH supplementation therapy. Anat Rec Part A 278A:561โ570, 2004. ยฉ 2004 WileyโLiss, Inc.