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

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