Journal of Clinical Endocrinology and Metabolism vol:75 issue:5 pages:1298-302
Serum levels of GH-binding protein (GH-BP) and insulin-like growth factor-I (IGF-I) were measured in 14 adolescent girls with Turner's syndrome (TS) before and during treatment with recombinant human GH (rhGH) and oral ethinyl estradiol (EE2). Before treatment, the mean +/- SE GH-BP level in TS patients was 33.2 +/- 2.0%; this was higher (P < 0.05) than that in bone age-matched (27.9 +/- 1.1%; n = 13) or chronological age-matched (28.1 +/- 0.8%; n = 17) control girls. The mean +/- SE IGF-I level in TS girls (283 +/- 26 micrograms/L) was comparable to that in bone age-matched controls (255 +/- 17 micrograms/L), but lower (P < 0.005) than that in chronological age-matched pubertal controls (568 +/- 35 micrograms/L). In 7 TS girls treated with daily sc injections of rhGH in a dose of 0.8 U/kg.week for 18 months, serum levels of IGF-I increased from 330 +/- 39 to 707 +/- 48 micrograms/L after 3 months of treatment and remained elevated for the entire observation period (P < 0.002). In contrast, GH-BP levels did not change significantly. In 7 other TS girls, puberty was induced after 2 yr of daily sc injections with rhGH (1 U/kg.week) by adding 100 ng/kg.day EE2, orally, during ongoing rhGH therapy. During 18 months of pubertal induction, serum GH-BP levels increased gradually from 31.4 +/- 2.7% at the start of EE2 treatment to a maximum of 49.2 +/- 0.8% after 1 yr (P < 0.001). Serum IGF-I levels, in contrast, did not change significantly. These results show that in adolescent TS patients 1) pretreatment serum GH-BP levels are higher than in bone age-matched or chronological age-matched control girls, and IGF-I levels are similar to those in bone age-matched but lower than those in chronological age-matched controls; 2) during rhGH treatment GH-BP levels do not change, whereas IGF-I levels increase significantly; and 3) oral EE2 treatment during ongoing rhGH treatment increases GH-BP levels markedly, but does not modify IGF-I levels.