Evaluation of surgery for acromegaly: role of intraoperative growth hormone measurement?

Abstract

Objective: Intraoperative growth hormone (GH) measurement has earlier been tried to improve surgery for acromegaly. We calculated GH half-life after adenomectomy and evaluated the possible role of this variable in predicting the final outcome of pituitary surgery in 28 consecutive patients with acromegaly. The sensitivity, specificity and predictive values were determined in relation to the results from GH suppression during an oral glucose load and IGF-1 3 months postoperatively. The GH half-life data were also compared to the corresponding results obtained from GH measurements between 60 min and 180 min after adenomectomy, and early, within 1 week, postoperatively. Results: GH half-life 31 min was recorded in 8/13 cured patients but also in 2/15 unsuccessful cases. A mean GH concentration 4.4 mU/L between 60 min and 120 min after adenomectomy was found in 11/13 cured subjects but also in 3/15 not cured patients. A mean GH 4.0 mU/L between 90 min and 180 min was found in 11/13 cured and in 4/15 not cured patients. A mean early postoperative GH concentration 2.6 mU/L was noted in all 13 cured patients, but also in 2/13 unsuccessful cases. The specificity of early postoperative GH 2.6 mU/L was 100% compared to 62% for a GH half-life 31 min (p< 0.05) and 85% for the GH mean values between 60 min and 120 min and 90 min and 180 min, respectively. The sensitivity for persistent disease of values above the four cut-off limits used was between 73% and 87%. The positive predictive value for a mean early postoperative GH value > 2.6 mU/L was 100%, and 72% for a GH half-life > 31 min (n.s.). Conclusion: Although intraoperative GH half-life might be useful in some cases, it was not a reliable tool for predicting outcome of pituitary surgery in acromegaly. In cases with a 50% decrease of a basal GH concentration > 5.5 mU/L, mean GH values 4 to 4.4 mU/L late intraoperatively were more informative but not as good as those obtained from the mean of a series of GH values drawn on one occasion within 1 week postoperatively, offering a 100% specificity for cure if 2.6 mU/L. Intraoperative GH half-life measurements should therefore be used with caution. The predictive values of the cut-off limits used in this study should be further evaluated before general application.