SURG-91. Sex differences in lactotroph adenomas: Tumor size and prolactin predict postoperative outcomes

INTRODUCTION Lactotroph pituitary adenomas are the most common secretory pituitary tumors, comprising 30-50% of functional adenomas [1]. Although dopamine agonists (i.e., cabergoline) are first-line therapy, surgical management is occasionally required. Notable sex-based differences in lactotroph adenomas remain incompletely characterized. Objective: To compare tumor size, prolactin levels, and long-term outcomes in males versus females with lactotroph pituitary adenomas. METHODS After Institutional Review Board Approval, we performed a retrospective review of all prolactin-secreting pituitary adenomas treated surgically at our institution over a 10-year period. Categorical and continuous variables were compared using the Chi Square test and Student’s T-test, respectively. RESULTS A total of 31 patients were included, of which 15 (48.4%) were female. Common surgical indications included acute vision loss (n=9), dopamine agonist intolerance (n=6), and patient preference for surgery (n=4) with no differences between sexes (p=0.28). Mean age was 45.6 years (21-81) with no difference between sexes. Compared to females, males had significantly higher preoperative prolactin levels (1036.8 vs. 218.8 ng/dL, p=0.0003) and significantly larger tumor size (16.3 cm3 vs. 1.01 cm3, p=0.0004). Furthermore, postoperative prolactin trended higher in males (113.8 vs. 56.0, p=0.08), with trends toward higher preoperative Knosp grade (Knosp ≥3: 56.3% in males vs. 20% in females, p=0.08) and residual tumor (56.3% vs. 20%, p=0.08). Tumor volume (p=0.0009), preoperative prolactin (p=0.001), and postoperative prolactin (p-0.003) were predictors of residual disease and need for postoperative cabergoline in univariate analysis. Receiver operating curves (ROC) analysis found preoperative prolactin >596 ng/mL (AUC 0.85) and tumor volume >3.14 cm3 (AUC 0.80), predicted need for postoperative cabergoline. CONCLUSION Lactotroph adenomas in males had significantly greater preoperative prolactin levels and tumor size, both predictive of incomplete resection and need for continued postoperative cabergoline. Our data represent further evidence that male lactotrophs are more aggressive and treatment-refractory compared to female lactotrophs.