Histologic, Ultrastructural, and Hormonal Characterization of a Pituitary Tumor Secreting Both hGH and Prolactin1

Abstract

An eosinophilic adenoma was removed transsphenoidally from a 5-yr-old female child with acromegalic gigantism. Pre-operatively, elevated serum levels of both growth hormone (hGH) and prolactin (HPr) were present that were responsive, in parallel, to both TRH (increased) and L-dopa (decreased). Oral glucose, chlorpromazine or medroxyprogesterone did not suppress hGH or HPr levels. Morphologic examination of the tumor demonstrated the presence of both somatotrophs and lactotrophs by differential staining (Herlant's tetrachrome technique) and by electron microscopy. In addition, cells appearing poorly granulated by light microscopy were revealed as actively secretory degranulated lactotrophs or somatotrophs by electron microscopy. In vitro biosynthesis was studied by incubating the tumor with ³H-l,4,5-leucine and immunoprecipitating the radioactive proteins released into the media at 4 and 24 hr with specific antisera to growth hormone and ovine prolactin. Radioactive proteins were precipitated to an equal degree by both antisera, indicating active synthesis of both hGH and HPr. Concentrations of hGH and HPr in the incubation media were also determined by radioimmunoassay. The tumor demonstrated increased production of hGH and particularly HPr when compared to normal pituitaries and to pituitary tumors from a patient with acromegaly and a patient with galactorrhea. These studies indicate that a human pituitary tumor with the capability for increased secretion of at least 2 hormones can occur, a situation previously firmly documented only in rodents. The tumor tissue in this patient was responsive to hypothalamic stimulation. Responses to L-dopa and TRH were excessive and for hGH paradoxical.