HIGH-AFFINITY GROWTH-HORMONE BINDING-PROTEIN IN PLASMA OF PATIENTS WITH ACROMEGALY AND THE EFFECT OF OCTREOTIDE TREATMENT

OBJECTIVE The objective of this study was to investigate the effect of plasma GH-levels on the high affinity growth hormone binding protein (GHBP). PATIENTS We studied plasma samples of eight patients with acromegaly and eight age and sex matched healthy subjects. DESIGN Patients with acromegaly were treated with octreotide administered by continuous subcutaneous infusion. Levels of growth hormone binding protein (GHBP) were measured in plasma samples before therapy and 3, 6 and 12 months after starting treatment. During this period, octreotide was administered in doses of 300-800 mug/day. The mean dose per patient over the study period ranged from 300 to 575 mug/24 h. The GHBP levels of patients with acromegaly were compared with those in the healthy subjects. MEASUREMENTS Bound and free I-125-GH in plasma were measured using FPLC gel chromatography on a Superose 12 column, after an overnight incubation period. The binding data were used for a Scatchard plot analysis. Wilcoxon's signed rank test was used for statistical analysis. RESULTS We found lower GHBP levels in acromegalic patients (P = 0.01) than in the control subjects. Octreotide treatment resulted in IGF-I levels <300 mug/l in four patients. In these patients GHBP levels increased. CONCLUSIONS We conclude that growth hormone binding protein levels are down regulated in acromegaly, indicating an important role for GH in the regulation of this protein.