To investigate the effect of recombinant hGH treatment on the growth rate and proportion of individuals with achondroplasia and hypochondroplasia, we studied 15 individuals with these common skeletal dysplasias. The study lasted 24 months and included 6 months of observation, 12 months of hGH therapy (0.04 mg/kg.day), and 6 months of posttreatment growth rate determination. In achondroplasia, the mean growth rate during the hGH treatment (5.3 +/- 1.6 cm) was significantly increased compared with that during the pretreatment (4.0 +/- 1.0 cm.yr, P < 0.01)) and posttreatment periods (3.1 +/- 1.3 cm; P < 0.001). In the 4 children with hypochondroplasia, the growth rate during hGH treatment was 7.0 +/- 2.4 cm/yr and 4.9 +/- 1.5 cm/yr during the pre- and posttreatment periods, respectively. In achondroplasia, there was a significant increase in growth rate of only the lower segment (from 1.1 +/- 1.6 cm/yr to 3 +/- 1.2 cm/yr, P < 0.02). There was no significant acceleration in the growth of the upper segment and of the scanogram measurements of the long bones. No untoward effects were noted. Recombinant hGH increases short-term growth velocity in children with achondroplasia/hypochondroplasia. Unexpectedly, this treatment does not seem to have a lesser effect on limbs than on trunk growth rate and, therefore, during 1 yr of treatment, does not increase body disproportion.

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