We aimed to evaluate the effects of estradiol (E2) upon the components of the IGF-I-IGFBPs axis in children clinically classified as short stature with(Group I, n=8) or without (Group II, n=23) growth hormone (GH) deficit. These patients are part of a double blind, placebo-controlled study to evaluate E2 effects on GH secretion provocative tests (see Martinez et al at this meeting). IGF-I was measured by RIA after acid-ethanol extraction and crioprecipitation of its IGFBPs. rhIGF-I was used as standard and tracer; the antiIGF-I UBK487 antibody was kindly provided by Dr. L. Underwood. IGFBP3 was measured by IRMA (DSL). The IGFs total binding capacity (BC) was measured according to Cailleau et al. (Mol Cell Endoc 69: 79, 1990). Results (mean± SEM): Table In Group I patients the frequency of abnormal IGFBP3 values was 6/8 (without E2) and 5/8 (with E2); in Group II it was 1/17 (with and without E2). Conclusions: IGFBP3's specificity to define short stature without GH deficit was 94% (with or without E2). E2 significantly increased IGF-I and IGFBP3 levels in Group II children without any changes in BC. This might be compatible with an increased GH secretion accompanied by a reduction in IGFBP2 levels. E2 only increased IGFBP3 levels in Group I children. This effect, probably GH independent, might be accompanied by an increase of specific IGFBP3 protease activity.

Table 1
Full size table