Multihormonal activities of normal and neoplastic pituitary cells as indicated by immunohistochemical staining

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Abstract
The hormonal changes during the course of induction and subsequent growth of mouse thyrotropic tumors and rat mammotropic tumors were studied by means of immunohistochemical staining in consecutive sections cut at 3γ. Multihormonal activities were detected in the primary tumors, but were more conspicuous in the transplanted neoplasms. Labelled anti‐thyrotropic hormone stained slightly normal gonadotropes. This is due to the presence of a common antigenic subunit between the two hormones and may explain the earlier finding of biologic gonadotropic activity in thyrotropic tumor‐bearing mice with high serum thyrotropic hormone levels. Antiserum to the β subunit of thyrotropic hormone stained the thyrotropes almost as intensely as did antiserum to the complete hormone. Neoplastic thyrotropes often had somatotropic activities. Neoplastic mammotropes usually had somatotropic, and less often, adrenotropic activities. Derangement of the hormonal spectrum of pituitary tumors is best related to the derepression of the cytogenetic code of differentiated normal cells. The rare findings of multihormonal activities in normal pituitary cells and the possible existence of a stem cell remain to be fully investigated.