Human nonfunctioning pituitary adenomas (NFPA) may produce CG in addition to the classical glycoprotein hormones (LH, FSH, and TSH). The aim of the present study was to localize LH β, FSH β, TSH β, α-subunit (α SU), CG, and its β-subunit (β SU) in NFPA using a highly specific immunohistochemical technique. Nine NFPA, obtained at surgery, were processed for both electron μscopy and immunohistochemistry. Three tumors resulted oncocytomas, and six were null cell. Using an immunofluorescence technique, all tumors were positive for at least one glycoprotein; in particular, seven adenomas were markedly positive for CG β, whereas only two were positive for the intact CG. No association among LH β, FSH β, and CG β positivity could be demonstrated in the different adenomas. In the seven tumors positive for both CG β and α SU, double fluorescence labeling demonstrated that six cases localized CG β and α SU in different cells, but only one tumor showed the two subunits colocalized in the same cells. These data confirm that pituitary tumors synthesize both α SU and β SU of glycoprotein hormones; in particular, the present study indicates that the majority of NFPA is able to synthesize CG, particularly its β SU. Moreover, the localization of CG β and α SU in different tumoral cells might account for the preferential expression of β SU and α SU instead of the intact hormonal molecules in NFPA.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical