17BetaHSD type 1 gene expression was detected in 34 of 42 adenomas in all tumor subtypes; 17betaHSD type 2 mRNA was detected in 18 of 42 adenomas, but not in prolactinomas; 17betaHSD type 3 mRNA was detected in 12 of 42 adenomas, but not in corticotropinomas; 17betaHSD type 4 was expressed in 20 of 42 adenomas by all adenoma subtypes.