Endocrine Abstracts

JOINT3484

Introduction: Pituitary adenomas (PAs) represent one of the three main characteristic endocrine tumors associated with multiple endocrine neoplasia type 1 (MEN1) syndrome and are presumed to have a more aggressive behavior compared to incidentally found PAs. In this study, we aim to emphasize the long-term evolution of non-functioning pituitary microadenomas (micro-NFPAs) in MEN1 patients.

Methods: We conducted a retrospective cohort study that included all adult index patients with a clinical diagnosis of MEN1 syndrome and micro-NFPAs, that were evaluated in our clinic at the Romanian National Institute of Endocrinology, C.I.Parhon’’, between January 1^st 2018 and 31^st December 2024. We sought to investigate the evolution of micro-NFPAs with a focus on tumor growth and pituitary function. We defined tumor growth or regression as a minimum 20% change in size compared to baseline.

Results: We identified 68 MEN1 patients that associated PAs, 18 macroadenomas and 50 microadenomas, of which 39 (78%) were non-functioning. 76.9% were females, with a mean age at diagnosis of 52.1 ± 13.2 years. The maximum tumor diameter at baseline was 5.1 ± 1.7 mm, without differences between sexes. No cystic lesions, hypopituitarism or visual field deficit were observed at baseline. Micro-NFPAs were associated with hyperparathyroidism or entero-pancreatic tumors in 69.2% and 15.4% of cases, respectively, all three classical, P’’s being accounted for in 15.4% of patients. Micro-NFPAs were the first MEN1 component diagnosed in only 12.8% of cases, more frequently being discovered ensuing MEN1 screening, following hyperparathyroidism (51.3%) or entero-pancreatic neuroendocrine tumors (NETs) (30.8%) diagnosis. More than half of patients (53.8%) were reassessed through imaging and pituitary function testing. Over a median follow-up duration of 6 years (interquartile range: 3.9-9), only 1 patient (2.6%) had significant tumor enlargement, while 28.2% regressed and 23.1% were stable. None developed new pituitary insufficiency. No predictors were identified for tumor growth. Patients with tumor reduction were older (P = 0.06), had larger tumor diameters at diagnosis (P = 0.038) and pathogenic MEN1 gene mutations on genetic tests (mostly Sanger sequencing, P = 0.014) compared to those whose tumors were stable or progressed. However, logistic regression found none of these factors to be significant predictors of tumor shrinkage.

Conclusion: Micro-NFPAs in MEN1 syndrome are generally discovered through screening following the diagnosis of hyperparathyroidism or entero-pancreatic NETs and have a benign course over long follow-up intervals.