Immunohistochemical colocalization of growth hormone (GH) and α subunit in human GH secreting pituitary adenomas

Summary

This immunohistochemical study disclosed that 9 of 15 GH secreting pituitary adenomas contained α subunit positive cells. These cases also contained PRL positive adenoma cells, but LHβ was negative. Of these 9 cases, 4 cases showed occasional FSHβ containing cells, 2 of these also contained a few TSHβ positive cells. By mirror section technique, variable numbers of adenoma cells were found to contain both GH and α subunit. Immunoelectron microscopically, both GH and α subunit were localized in secretory granules which suggested their co-release from the tumour cells. The presence of GH and α subunit in rough endoplasmic reticulum indicated their active production in the tumour. In the normal adult anterior pituitary gland, about 10% of GH cells contain FSH α,β and LHβ subunits and had appearances suggesting the co-production of GH and FSH as well as LH. The colocalization of GH and FSH α is considered to be associated with the neoplastic transformation GH cells which possess the intrinsic potentiality of differentiation toward α subunit. However, the mechanism for the lack or deficiency ofβ subunits in the neoplastic condition remains to be further investigated.