Objective: To investigate the relationship with MR signal intensity and histological types of pituitary adenomas. Methods: MR images of 167 patients with pituitary adenomas including 20 growth hormone (GH) adenomas

114 prolactin (PRL) adenomas

30 non-secretory adenomas

2 adrenocorticotropic hormone (ACTH) adenomas and 1 thyroid-stimulating hormone (TSH) adenoma were reviewed retrospectively. The relationship between MR signal intensity and homogeneousness with histological types of pituitary adenomas were analysed. Results: MR signal intensity was correlative with histological types of adenoma. GH adenomas were usually equally intense (63.6%

69.2%) in T1WI and T2WI; PRL macroadenomas were less

slightly less

or equally intense less (20.8%

16.9%

45.3%) in T1WI and slightly more or more intense (74%

14%) in T2WI; PRL microadenomas were less

slightly less or equally intense (22.2%

70.8%) in T1WI and slightly more or more intense (30.6%

56.9%) in T2WI; non-secretory adenomas were less

slightly less

or equally intense (17.6%

14.7%

55.9%) in T1WI and slightly more or more intense (61.8%

32.4%) in T2WI. Hemorrhage of adenomas was mostly found in GH adenomas (22.2%) and PRL adenomas (21.4%). Conclusion: The distinguished histological types of adenomas can be differentiated by MR signal intensity; hemorrhage of adenomas is mostly found in secretory adenomas.