Response to long-term growth hormone therapy in short children with reduced GH bioactivity.

Background/Aims: The aim of the present study was to investigate whether short children with normal growth hormone (GH) immunoreactivity, but reduced bioactivity (bio-inactive GH) could benefit from rhGH treatment as GH deficient (GHD) patients. Methods:We evaluated 12 pre-pubertal children (8 M, 4 F), with GH deficiency-like phenotype showing normal serum GH peak levels > 10 ng/ml), measured by immunofluorimetric assay (IFMA-GH), in contrast with a reduced GH bioactivity (bio-GH), evaluated using the Nb-2 cells. We also evaluated 15 age-matched GHD pre-pubertal children (11 M, 4 F) with serum GH peak < 5 ng/ml. Both groups were treated with rhGH therapy at the dose of 0.23 mg/kg/week s.c. Results: Serum bio-GH/IFMA-GH ratio at peaktime for each patient during the provocative test was significantly lower in bioinactive GH than in GHID children (0.29 vs. 2.05, p = 0.00001). Recombinant human GH therapy induced a significant (p < 0.001) increase in growth rate in both groups during the first 2 years. In the third year of treatment, while growth rate in GHD children is maintained, in bioinactive GH patients it decreases remaining, however higher compared to the pre-treatment one. Conclusions: Short rhGH therapy given to selected bioinactive GH children improve growth rate and might result in greater final adult height.