Differential effects of octreotide treatment and transsphenoidal surgery on growth hormone-binding protein levels in patients with acromegaly

Object. The high-affinity growth hormone-binding protein (GHBP) represents the extracellular portion of the growth hormone (GH) receptor, and its seru m levels are a reflection of the tissue receptor status. Levels of GHBP are decreased in patients with active acromegaly, probably because of downregu lation of GH receptors. However, there are no studies of patients with acro megaly in which the effects of medical (that is, administration of somatost atin analogs) and surgical therapy on GHBP levels have been compared. That is the task the authors set out to accomplish in this study. Methods. The authors studied seven patients in whom acromegaly had been rec ently diagnosed. They examined these patients at baseline, 2 months after o ctreotide treatment (subcutaneous administration of 100 mu g octreotide thr ee times per day), and 1 month after transsphenoidal surgery. Growth hormon e-binding activity was measured, as well as the following biochemical marke rs of the somatotropic axis: GH suppression induced by oral administration of glucose, insulin-like growth factor-I (IGF-I), and Insulin-like growth f actor-binding protein-3 (IGFBP3). Although octreotide treatment induced a d ecrease in the levels of GH, IGF-I, and IGFBP3, as well as an increase in t he level of GHBP, these biochemical markers did not reach normal levels. On the other hand, after transsphenoidal surgery, GHBP levels became normal, particularly in those patients in whom serum GH could be suppressed to an u ndetectable level after glucose loading. Conclusions. The authors conclude that persistently low GHBP levels in pati ents with acromegaly are normalized by successful pituitary surgery and cor relate well with disease activity.