Male prolactin secreting pituitary adenomas in humans studied by peroxidase-labelled antibody method.

In order to identity the source of excess secretion of prolactin in male patients, the pituitary tumors of 11 males with hyperprolactinaemia were studied by peroxidase-labelled antibody method using antibodies against human prolactin. Using light microscope, prolactin was demonstrated in most tumour cells in all cases. Ultrastructurally, prolactin was localized mainly on the secretory granules. Immunohistochemically positive cells were thought to correlate with first type of tumour cells which were the major component observed by regular electron microscopic study without immunohistochemical staining. These findings indicated the secretion of excess amount of prolactin by the tumour cells and were considered to be responsible for the category of Male Prolactin Secreting Pituitary Adenoma. The mechanism by which these male hyperprolactinaemic patients are endocrinologically non-functioning is also discussed.