Magnetic resonance imaging phenotypes of GH-secreting pituitary adenomas and correlation with hormonal burden and clinical severity

Abstract Background Magnetic resonance imaging (MRI) is central to anatomical evaluation of growth hormone (GH)–secreting pituitary adenomas with increasing evidence suggesting that MRI characteristics may also reflect tumour biology and disease severity. Objective To analyse MRI-based phenotypic features of GH-secreting pituitary adenomas and examine their relationship with hormonal burden, clinical presentation, and tumour invasiveness. Methods This retrospective observational study was conducted over a period of five years at a tertiary care referral centre. A total of 165 patients with biochemically confirmed acromegaly who underwent pre-treatment contrast-enhanced pituitary MRI were included. Imaging was performed using a 1.5T scanner with a dedicated seller protocol. Tumours were assessed for size, suprasellar extension, cavernous sinus invasion (using Knosp grading), Hardy classification, T2-weighted signal characteristics, and internal cystic or necrotic components. Two experienced radiologists independently reviewed all scans. Baseline GH and IGF-1 levels were recorded, and clinical data including visual field defects and headache were analysed. Multivariate logistic regression was used to identify independent predictors of tumour invasiveness. Results Macroadenomas accounted for 86.1% of cases, with cavernous sinus invasion observed in 38.2% and suprasellar extension in 41.8%, indicating a predominance of advanced disease at presentation. Larger tumours were associated with significantly higher GH and IGF-1 levels. Invasive adenomas (Knosp grade ≥ 3) demonstrated greater hormonal activity compared to non-invasive tumours. T2 hyperintensity was the most common signal pattern and was independently associated with invasive behaviour. Cystic or necrotic changes were identified in approximately one-third of tumours. Radiological severity correlated closely with clinical symptoms, particularly visual field defects and headache. Conclusion MRI phenotyping in acromegaly provides valuable insight into tumour biology, hormonal burden, and clinical severity. Larger, invasive, and T2-hyperintense adenomas represent a more aggressive disease phenotype associated with greater endocrine activity and neurological symptoms.