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

摘要

OBJECT: The high-affinity growth hormone-binding protein (GHBP) represents the extracellular portion of the growth hormone (GH) receptor, and its serum levels are a reflection of the tissue receptor status. Levels of GHBP are decreased in patients with active acromegaly, probably because of downregulation of GH receptors. However, there are no studies of patients with acromegaly in which the effects of medical (that is, administration of somatostatin 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 recently diagnosed. They examined these patients at baseline, 2 months after octreotide treatment (subcutaneous administration of 100 microg octreotide three times per day), and 1 month after transsphenoidal surgery. Growth hormone-binding activity was measured, as well as the following biochemical markers of the somatotropic axis: GH suppression induced by oral administration of glucose, insulin-like growth factor-I (IGF-I), and insulin-like growth factor-binding protein-3 (IGFBP3). Although octreotide treatment induced a decrease in the levels of GH, IGF-I, and IGFBP3, as well as an increase in the 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 undetectable level after glucose loading. CONCLUSIONS: The authors conclude that persistently low GHBP levels in patients with acromegaly are normalized by successful pituitary surgery and correlate well with disease activity.