Morphometric study of normal and adenomatous pituitary somatotrophs in humans.

Somatotrophs from ten pituitary adenomas were evaluated morphometrically by light and electron microscopy using the following parameters: a) nuclear, cytoplasmic and cell volumes; b) volume density, total volume, surface density, total surface and surface/volume ratio of secretory granules, mitochondria, rough endoplasmic reticulum and Golgi apparatus, and c) the number of secretory granules and mitochondria per micron3 of cytoplasm and per cell. The results were compared (p less than 0.05 and p less than 0.10) with those obtained from somatotrophs identified in five normal pituitaries. The data obtained indicate that: a) in the adenomas, the number of secretory granules per cell cannot be accurately evaluated from their apparent number in sectioned cell profiles; b) there are two basic sub-types of adenomatous somatotrophs defined according to the mean secretory granule diameter; cells in which granule diameter is inferior to 180 nm exhibit distinct morphological features such as nuclear pleomorphism, the presence of gross bundles of intermediate sized filaments or fibrous bodies in the cytoplasm and a variable number of secretory granules. Adenomas constituted mainly by these cells were found in younger patients, suggesting the more aggressive nature of these tumours, thus warranting close clinical follow-up of such patients; and c) in both types of adenomatous cells, the organelles directly involved in the secretory process, i.e., the rough endoplasmic reticulum and Golgi apparatus, are larger than in the control cells; however, the ratio between the surfaces of these two compartments does not differ among the three groups studied.