Baseline MRI findings as predictors of hypopituitarism in patients with non-functioning pituitary adenomas

Hypopituitarism tends to occur in large pituitary adenomas. However, similar tumors could present with strikingly different hormonal deficiencies. In this study, we looked at MRI characteristics in non-functioning pituitary adenomas (NFPA), which could predict secondary adrenal insufficiency (SAI) and central hypothyroidism (CHT). We reviewed the files of patients with NFPA attending our clinic. Tumor size, invasiveness, MR-signal intensity, and gadolinium enhancement in preoperative MRI were recorded along with documented presurgical hypopituitarism profile. Logistic regression was used to predict SAI, CHT or both (SAI/CHT) based on MRI and demographic parameters. Receiver operating characteristic curves were used to determine their diagnostic utility. 121 patients were included. Older age (P=0.021), male sex (P=0.043), stalk deviation (P<0.0001), contrast enhancement (P=0.029) and optic chiasma compression (P=0.012) were associated with SAI/CHT. Adenoma vertical height, largest diameter, and estimated volume were also strongly associated with SAI/CHT (P<0.0001). These associations remained significant in a multivariate analysis. No tumor smaller than 12mm in vertical height, 17mm in largest diameter, or 0.9 cm3 in volume was associated with SAI/CHT. At cutoff >18mm for vertical height, >23 mm for largest diameter, and >3.2 cm3 the sensitivity was around 90-92% for detecting SAI/CHT. Only vertical height was significantly associated with any one or more pituitary hormonal deficit (P=0.001). In conclusion, adenoma size, independent of the measurement used, remains the best predictor of SAI/CHT in NFPA. Dynamic testing to rule out SAI is probably indicated in adenomas larger than 18 mm vertical height, 23 mm largest diameter and 3.2cm3 adenoma volume.