Extracellular growth hormone deposits in pituitary adenoma

Ultrastrucutral examination of 184 pituitary adenomas demonstrated the presence of extracellular accumulations of electron dense material in 3 out of 64 cases with acromegaly. Fibrillary structures were seen in larger deposits of such material. This material was only observed in biopsies fixed directly with osmium tetroxide; initial fixation with glutaraldehyde did not retain the material and left empty spaces. Positive immuno-histochemical reaction with specific antibodies demonstrated that the extracellular material contained growth hormone (GH). The presence of this extracellular material could not be related to the age or sex of the patient nor to the duration of symptoms, size of the tumor, presence of diabetes mellitus, or concomitant secretion of prolactin. The pericapillary fibrous sheath was heavily thickened in the patient with the longest duration of symptoms, intermediate in thickness in the second and normal in the third.