Electron microscopical morphometry of GH producing pituitary adenomas in comparison with normal GH cells

GH producing adenomas of patients with acromegaly (undifferentiated acidophil adenomas and well differentiated GH cell adenomas) were studied at the ultrastructural level and analysed morphometrically by the point counting method. They were compared with identically prepared GH cells of normal pituitaries from patients undergoing surgery for metastasizing cancer of the prostate. In the well differentiated GH cell adenomas significantly more points were counted on nucleoli, unorganized cytoplasm, rough endoplasmic reticulum, immature secretory granules, Golgi areas and on the plasma membranes, than in normal GH cells. Comparison of normal GH cells with tumour cells in undifferentiated acidophil adenomas demonstrated significantly larger volumes of nuclei, rough endoplasmic reticulum, Golgi fields, immature secretory granules and of the cell membranes, and also of nucleoli and of the mitochondria. Secretory granules and lysosomes were observed more frequently than in normal GH cells. In a comparison of both adenoma types, the well differentiated acidophil adenomas contained significantly larger volumes of the unorganized cytoplasm, secretory granules and of cell membranes, whereas more points were counted on the rough endoplasmic reticulum and on the mitochondria in undifferentiated acidophil adenomas. The differences between the normal GH cells and the GH cell in undifferentiated adenomas (mainly larger nucleoli, larger volumes of the rough endoplasmic reticulum and the lower volumes of secretory granules) indicate a higher secretory activity in the adenomas. The significant differences between the well differentiated and the undifferentiated adenomas (mainly the increased volumes of mitochondria and of the unorganized cytoplasm in the undifferentiated tumours) indicate a lower grade of differentiation and may be interpreted as signs of increased proliferation.