Predicting Long-term Remission by Measuring Immediate Postoperative Growth Hormone Levels and Oral Glucose Tolerance Test in Acromegaly

The suppression of the growth hormone (GH) on an oral glucose tolerance test (OGTT) has been accepted as the most reliable parameter for determining remission of acromegaly.To evaluate the role of immediate postoperative GH level and 1-week postoperative OGTT as early predictive tools of long-term surgical remission.One hundred ninety-four acromegalic patients who received transsphenoidal tumor resection and were followed up for > 1.5 years (3.80 ± 0.17 years) with at least 3 postoperative OGTTs were evaluated. Level of GH was measured 2, 6, 12, 18, 24, 48, and 72 hours postoperatively, and an OGTT was performed 1 week after surgery, every 6 months for the first 3 years, and annually thereafter.One hundred seventy-seven patients underwent gross total resection; long-term remission was achieved in 153. The GH level at 24 hours after surgery showed the highest predictive power for long-term remission. Long-term remission was maintained in 125/127 (98.4%) patients who had nadir GH levels < 1.0 μg/L on an early postoperative OGTT. However, when nadir GH levels were > 1.0 μg/L on an early postoperative OGTT, long-term remission was observed in 28 patients (28 of 67, 41.8%) in a delayed fashion. One-week postoperative OGTT had a sensitivity of 81.7% and specificity of 95.1% for predicting remission.Immediate postoperative GH level is a very good predictor of long-term outcome in acromegaly. One-week postoperative OGTT is also a good predictor with high specificity. These findings may provide critical information for the determination of adjuvant treatment after surgery.