Predictive Value of Early Postoperative Growth Hormone Levels in Determining Long-Term Biochemical Cure of Acromegaly

Introduction: Using strict biochemical remission criteria, the authors assessed surgical outcomes after endoscopic transsphenoidal resection of growth hormone (GH)-secreting pituitary adenomas and identified the predictive value of early postoperative GH levels in determining disease remission.

Methods: A retrospective review of a prospectively maintained database was performed. A total of 35 endoscopic procedures for adenoma resection were reviewed. The average duration of follow-up was 30.7 months. In the postoperative period, growth hormone levels were obtained immediately postsurgically, and on each postoperative day (POD). The thresholds of an age-appropriate, normalized insulin-like growth factor-1 (IGF-1) concentration, a nadir GH level after oral glucose load of less than 1.0 μg/L, and a random GH level of less than 2.5 μg/L were required to establish biochemical cure postoperatively.

Results: Following 45.7% of the operative procedures (16 of 35), an endocrinological cure was achieved. Preoperative GH and IGF-1 levels were not significantly different in those patients who achieved biochemical cure (Group A) and those who did not (Group B). Although, the immediate POD#0 levels were not significantly different, a lower level was achieved on each subsequent POD and noted as early as POD#1 (A: 1.2 ± 0.7 μg/L, B: 4.2 ± 3.8 μg/L, P = 0.0003) and POD#2 (A: 1.2 ± 0.7 μg/L, B: 5.8 ± 7.2 μg/L, P = 0.0001). In those patients in whom a biochemical cure was attained, nearly all had a GH level < 2.4 μg/L on POD#1 and later. The one exception was a patient with a recurrent adenoma, two previous resections, a preoperative GH level of 9.5 μg/L, and a POD#1 level of 3.0 μg/L. On POD#2, the level had decreased to 1.6 μg/L and continued to decline. In this cohort, the use of a postoperative GH < 2.5 μg/L on POD#1 and later as a predictor of future biochemical remission resulted in a specificity of 100% and a sensitivity of 74%.

Conclusion: Following surgical resection, GH levels may decrease to acceptable levels as early as the first postoperative day. The measurement of growth hormone levels in the immediate preoperative period may be helpful in predicting future biochemical remission. Used in conjunction with intraoperative findings and postoperative imaging, obtaining early postoperative GH levels could potentially identify those patients who require additional treatment, including early revision surgery, medical therapy, and radiation.