Glucocorticoids have multiple actions, including a suppressive feedback eff
ect on pituitary corticotrophs via the glucocorticoid receptor (GR). By imm
unocytochemistry, we studied GR expression in 86 surgically removed various
pituitary adenoma types. Ten cases contained nontumorous pituitary fragmen
ts, which were suitable for immunocytochemical investigation. In addition,
30 autopsy-obtained pituitaries, 10 of them containing incidental microaden
omas, were examined as well. Using a polyclonal GR antibody, the streptavid
in-biotin-peroxidase complex method revealed nuclear and/or cytoplasmic GR
immunoreactivity in many nontumorous corticotrophs and other adenohypophysi
al cell types and in S-100 protein immunopositive stellate cells. Cellular
localization was confirmed by double immunostaining. Pars intermedia cortic
otrophs, posterior lobe axons, Herring bodies, and pituicytes as well as se
veral endothelial cells lining the capillaries were also immunopositive. CR
immunoreactivity was also demonstrated in many GH, PRL, ACTH, TSH, FSH, LH
a-subunit producing adenomas, null cell adenomas, and oncocytomas. The ext
ent and degree of immunostaining varied considerably from case to case. Sup
pressed corticotrophs showing the Crooke's hyaline change due to glucocorti
coid excess were present in the nontumorous pituitaries of patients with Gu
shing's disease and in those treated with pharmacologic doses of glucocorti
coids. Many suppressed nontumorous corticotrophs exhibited only weak or no
CR immunopositivity, indicating GR downregulation accompanied by cellular i
njury. Study of autopsy obtained pituitaries for GR yielded inconclusive re
sults indicating that autopsy obtained adenohypophyses are not suitable for
the immunocytochemical investigation of GR.