Secondary hormonal deficiency (SHD) in sellar masses (SM) is thought to be partly due to compression of the portal vessels by the enlarging tumour restricting the blood supply to the normal pituitary tissue. However, to date no study has looked at the patterns of SHD in various types of SM and assessed if SHD is related solely to the size of SM or is associated with the underlying pathology. We assessed 914 patients with SM enrolled in our comprehensive pituitary registry since November 2005 and analyzed the pattern of SHD at presentation in relation to tumour type and size at presentation. While there was an overall trend of a higher rate of SHD in larger SM (P<0.0001), the rates of SHD were significantly different in various types of SM despite similar size. The rates of SHD in SM < 9 mm were: Nonfunctioning adenoma [NFA] (10%), Prolactinoma (49%), GH adenoma (13%), ACTH adenoma (33%), craniophaygioma (50%), meningioma (0%) and Rathkes cleft cyst [RCC] (11%); 1019 mm were: NFA (35%), Prolactinoma (73%), ACTH adenoma (30%), GH adenoma (23%), craniopharyngioma (48%), meningioma (5%) and RCC (17%); 2029 mm were: NFA (64%), Prolactinoma (78%), ACTH adenoma (100%), GH adenoma (75%), meningioma (16%), craniopharyngioma (70%) and RCC (41%) and > 30 mm were: NFA (83%), Prolactinoma (100%), GH adenoma (80%), meningioma (27%) and craniopharyngioma (88%) (all P <0.001). Furthermore, of the two largest categories of SM, NFA have higher odds ratio (3.34; CI = 1.895.89) of presenting with multiple SHD when compared to prolactinomas, despite similarity in gender, age and size of the tumour (P<0.001). These novel data suggest that SHD patterns vary among different types of SM and are not solely dependent on tumour size. Our data also show that NFA are more likely to present with multiple hormonal deficiencies.