Abstract
To examine the potential causes for short stature in girls with Turner Syndrome, we explored the possibility that secreted GH in these girls may have decreased bioactivity. Twenty girls with Turner syndrome, ages 4.8 to 15.9 years and heights averaging −3.3 by SDS, had blood samples obtained every 20 min for 12 h overnight. An equal aliquot of each sample was pooled for each girl to measure GH by radioimmunoassay (RIA-GH) and esiradiol (E2). In each pool, in vivo GH bioactivity was estimated by measurement of the GH-dependent peptides, IGF-1 and IGF-binding protein 3 (IGFBP3). GH bioactivity was also measured in vitro by a newly developed GH bioassay that determined the ability of GH in serum to suppress the conversion of glucose to lipid in 3T3-F442A cultured adipocytes (B-GH; assay sensitivity of 1.25 μg/L GH or 6.25 μg/L GH in serum). Data were analyzed by regression after logarithmic transformation where appropriate. The correlation between RIA-GH and B-GH was 0.519; p = 0.02. IGF-1 and 1GFBP3 increased with increasing age but B-GH did not (r = 0.409, 0.695, and 0.017, respectively). The correlation of IGF-1 and B-GH was better than that for RIA-GH (r = 0.375 vs 0.03, respectively). For IGRBP3, the correlations between B-GH or RIA-GH were similar (r = 0.2). Neither B-GH, RIA-GH, IGF-1 or IGFBP3 correlated with height SDS. Four girls had measurable concentrations of E2 and were taller (SDS = −2.4 ± 0.6) than those without detectable E2 (SDS = −3.5 ±0.3). The girl with the greatest E2 concentration also had the greatest IGF-1, RIA-GH, and B-GH concentrations. In conclusion, B-GH correlates better with IGF-I than does RIA-GH, and the GH secreted in girls with Turner syndrome is bioactive as determined by in vitro measures (GH bioassay in adipocytes) and in vivo measures (IGF-1 and IGFBP3).
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Foster, C., Kletter, G., Hopwood, N. et al. CORRELATION OF GH BIOACTIVITY TO IGF-1 AND HEIGHT IN GIRLS WITH TURNER SYNDROME. Pediatr Res 33 (Suppl 5), S58 (1993). https://doi.org/10.1203/00006450-199305001-00328
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DOI: https://doi.org/10.1203/00006450-199305001-00328