Summary

Abstract

The original three cell type classification (eosinophilic, basophilic, chromophobe) of the pituitary has been invalidated by modern staining techniques and more recently by immunohistologic procedures. The resultant observations led to the establishment of the “one cell, one hormone” theory indicating that each pituitary hormone (somatotrophic, thyrotrophic, adrenocorticotrophic, melanotrophic, lactogenic) with the exeption of the two gonadotrophic hormones is produced by a particular cell type characterized by distinct staining properties. The two gonadotrophic hormones (follicle stimulating and luteinizing hormone) are probably produced by the same cell.—The ultrastructural examination of the normal human anterior pituitary led to the same conclusion. Differences in cell size and shape, number, distribution and morphology of granules in the cytoplasm and amount of rough-surfaced endoplasmic reticulum are all used to distinguish the individual cell types. The exact correlation of each hormone with its production site has been established only in experimental animals and no unanimity has been reached for all cell types in man. Several publications agree only in the description of three cells (somatotrophic, prolactin producing, thyrotrophic).—In addition to the six granulated hypophysial cells involved in hormone production there are nongranulated cells, which are involved in the delineation of the colloid containing follicles. These follicular cells have star-like processes which extend between the secretory cells. There is no evidence to suggest hormone production in the follicular cells. They seem to represent the only true chromophobe cell since the staining characteristics observed with modern staining methods is dependent upon the stored hormone granules.