Revisiting the Role of Insulin-like Growth Factor-1 Measurement after Surgical Treatment of Acromegaly

Context: In the management of growth hormone (GH)-secreting pituitary adenomas, the oral glucose tolerance test (OGTT) has been the gold standard not only for diagnoses but also for the determination of biochemical remission. Insulin-like growth factor-1 (IGF-1) is an essential biomarker, although it should be adjusted for both age and sex. Objective: We evaluated whether IGF-1 levels could serve as a reliable alternative to an OGTT for disease monitoring after the surgical treatment of acromegaly. We retrospectively reviewed the medical records of 320 patients who underwent surgical resection of their GH-secreting pituitary tumors at the Severance hospital. Receiver operator characteristic (ROC) analyses were performed to validate the accuracy of IGF-1 levels for the assessment of remission. In addition, regression analyses were performed to identify factors associated with discrepancy between OGTT and IGF-1 levels. Results: Except for 1 week after surgery, ROC analyses showed an area under the curve of greater than 0.8 for IGF-1 at all time points. Of 320 patients, 270 achieved endocrine remission after surgery alone. Among these patients, IGF-1 levels were normalized in 250 patients. The mean duration from surgery to IGF-1 normalization was 4.7 months. Regression analyses demonstrated that risk of failed IGF-1 normalization was increased by 3.1-fold when the tumor invaded the cavernous sinus and increased by 9.0-fold in patients with incomplete tumor removal. Conclusion: IGF-1 level is a reliable alternative to OGTT and plays a valuable role in monitoring acromegaly status.