Clinically Nonfunctioning Pituitary Incidentalomas: Characteristics and Natural History

Introduction: Available data on pituitary incidentalomas mostly derive from small-scale studies, with heterogeneous inclusion criteria and limited follow-up. No paper has focused specifically on clinically nonfunctioning pituitary in­cidentalomas (CNFPIs). Objective: To describe the charac­teristics and the natural history of patients diagnosed with CNFPIs. Methods: Retrospective multicenter cohort study evaluating hormonal, imaging, and visual field characteristics at diagnosis and during follow-up of CNFPIs investigated in 2 Pituitary Centers. Results: Three hundred and seventy-one patients were included (50.9% microadenomas, 35.6% males). Men were older and more likely to have a macroadenoma (p < 0.01). Totally, 23.7% of patients presented secondary hormonal deficits (SHDs), related to tumor size (higher in macroadenomas; p < 0.001) and age (higher in older patients; p < 0.001). Hypogonadism was the most frequent SHD (15.6%). Two hundred and ninety-six patients had follow-up data, 29.1% required surgery after first evaluation, and 97 had at least 3 years of follow-up. In total, 15.3% adenomas grew (more macroadenomas), but only in microadenomas patients with longer follow-up showed a higher growth trend. Totally, 5.2% of patients developed new SHDs (micro- vs. macroadenomas p = 1.000), and in 60% of them this was not associated with an increase in tumor size. Thirteen additional patients required surgery during follow-up (1 microadenoma at diagnosis). Conclusions: Macroadenomas and age are risk factors for SHD in CNFPIs, which occur at diagnosis in a quarter of patients. During follow-up, macroadenomas tend to grow more often, but microadenomas display higher growth trend as follow-up increases. Deterioration of pituitary function is not always related to adenoma growth.