Human
pituitary tumors are generally benign
adenomas causing considerable morbidity due to excess
hormone secretion,
hypopituitarism, and other
tumor mass effects.
Pituitary tumors are highly heterogeneous and difficult to type, often containing mixed cell phenotypes. We have used
calcium imaging followed by multiple immunocytochemistry to type
growth hormone secreting (GHomas) and non-functioning
pituitary adenomas (NFPAs). Individual cells were typed for stored
hormones and
calcium responses to classic
hypothalamic releasing hormones (HRHs). We found that GHomas contained
growth hormone cells either lacking responses to HRHs or responding to all four HRHs. However, most GHoma cells were polyhormonal cells responsive to both
thyrotropin-releasing hormone (TRH) and GH-releasing
hormone. NFPAs were also highly heterogeneous. Some of them contained
ACTH cells lacking responses to HRHs or polyhormonal gonadotropes responsive to
LHRH and TRH. However, most NFPAs were made of cells storing no
hormone and responded only to TRH. These results may provide new insights on the ontogeny of GHomas and NFPAs.