This study, carried out on 9 nonfunctioning pituitary adenomas, was undertaken in order to evaluate the ability of these tumors to synthesize and release gonadotropins and/or free a-subunit (a-SU) of glycoproteins. The morphological study included electron microscopy and immunofluorescence analysis while hormone release was evaluated by the reverse hemolytic plaque assay (RHPA) and measurements in culture media. By electron microscopy in all tumors (6 null cell adenomas and 3 oncocytomas), it was possible to identify rough endoplasmic reticulum, Golgi apparatus and secretory granules. By immunofluorescence, 5 of 6 tumors were immunoreactive for one or more gonadotropin subunits; in particular, 5 adenomas were positive for α-SU and LH-β, and 3 for FSH-β. By the RHPA, about 1% of cells obtained from one single tumor formed plaques for LH-α and β-SU while the remaining tumors were negative. Similarly, the study of media concentrations of LH, FSH and α-SU in 2 h culture revealed very low amounts of released hormones. In these experimental conditions no modification was observed after the addition of stimulatory agents such as TRH, GnRH and VIP. The present study clearly indicates that although the large majority of nonfunctioning tumors are positive for gonadotropins their secretory capacity is very low in both basal and stimulated conditions.
- electron microscopy
- Pituitary adenomas
- reverse hemolitic plaque
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism