6743 Decline in IGF-1 after surgery of the nonfunctioning pituitary neuroendocrine tumor

Abstract Disclosure: J. Sugata: None. S. Fujio: None. R. Makino: None. T. Hanada: None. R. Hanaya: None. Background: Patients undergoing surgical treatment for nonfunctioning pituitary neuroendocrine tumors (PitNET) may experience impaired secretion of growth hormone (GH). The optimal timing for assessing GH secretory function postoperatively remains unclear. In our department, we typically conduct hormone-loading tests three months after surgery. However, even in some cases without a diagnosis of growth hormone deficiency (GHD) at that point, there might be a gradual decline in Insulin-like growth factor-1 (IGF-1). Methods: We studied patients who exhibited peak GH levels > 1.8ng/ml in an insulin tolerance test (ITT) three months after undergoing surgery for nonfunctioning PitNET. We evaluated the levels of IGF-1 during the last observation, excluding cases where reoperation or radiosurgery was performed. Results: We identified 67 cases (29 males, 38 females) meeting the study criteria, with a median age of 54 years. The median follow-up time spanned 6 years (range 1-13 years). The median standard deviation (SD) scores of IGF-1 three months after surgery were -0.96, with 14 cases (21%) below -2.0 SD. At the end of the follow-up period, the median SD scores of IGF-1 were -1.31. This was significantly lower than the three-month time point (p<0.01), and 21 cases (31%) recorded were below -2.0 SD. In 6 cases suspected of severe GHD due to subjective symptoms or decreased IGF-1, ITT, or GH-releasing peptide-2 were retested. Among these, 2 cases were diagnosed with severe GHD, while the remaining demonstrated normal secretion of GH despite the low concentration of IGF-1. The IGF-1 SD scores at the end of follow-up and the three-month time-point exhibited a significant correlation (R2=0.74, p<0.01). However, no correlation was found between IGF-1 scores and peak GH concentration, age, tumor size, pituitary apoplexy, or preoperative IGF-1 SD scores. Conclusions: IGF-1 exhibited a progressive decrease in the majority of cases without severe GHD, with some cases showing reductions greater than -2.0 SD. Our findings emphasize the importance of cases with long-term clinical follow-up low IGF-1 after PitNET surgery, even when GH secretion appears normal. Presentation: 6/1/2024