High-affinity growth hormone (GH)-binding protein (GHBP), body fat mass, and insulin-like growth factor-binding protein-3 predict the GHBP response to GH therapy in adult GH deficiency syndrome

The study objective was to investigate which baseline factors can accuratel y predict plasma high-affinity growth hormone (GH)-binding protein (GHBP) l evels after GH replacement therapy in patients with GH deficiency (GHD). Th e study group consisted of 36 GHD patients (22 men and 14 women; mean age, 43.1 years; (range, 21 to 60) known to have adult-onset GHD for many years (range, 4 to 22). They were randomly divided into a GH-treated group (n = 1 9) and a placebo group (n = 17). Body composition (assessed by bioelectrica l impendence analysis [BIA]), plasma GHBP (fast protein liquid chromatograp hy [FPLC] sire-exclusion gel chromatography), insulin-like growth factor-I (IGF-I), and IGF-binding protein-a ([IGFBP-3] radioimmunoassays) were measu red before and after 6 months. A stepwise multiple linear regression analys is with the plasma GHBP level after 6 months as the dependent variable was used to unravel significant explanatory (or predictor) variables. In contra st to placebo therapy, GH replacement therapy increased the mean plasma lev els of IGF-I and IGFBP-3 to the normal range, whereas a small but statistic ally significant increase in plasma GHBP was observed. The combination of b aseline plasma GHBP, body fat mass, and IGFBP-3 predicts posttreatment GHBP revels accurately (adjusted R-2 = .97), indicating that baseline variables such as age, gender, fat-free mass, and IGF-l have no contribution. Furthe rmore, reliability analysis showed that the observed and predicted values f or GHBP fit a strict parallel model. These findings indicate that the varia tions in body fat mass and IGFBP-3 among adult GHD subjects explain the rep orted variable response of GHBP to GH replacement therapy. Copyright (C) 19 99 by W.B. Saunders Company.