2) The major exception to this rule is the reticulin stain, which is essential to distinguish normal adenohypophysial architecture, hyperplasia, and adenoma.
Some clinically silent tumors are recognized by electron microscopy as having gonadotropic differentiation, but some have characteristics of less well differentiated cells, resembling the "null" cells that were initially thought to be undifferentiated precursors of adenohypophysial cells.
Hyperplasia of adenohypophysial cells can give rise to clinical syndromes and even radiologic features that are indistinguishable from pituitary adenomas.
It has been reported by Cano et al (199) that Cd modifies expression of two major clock genes, period (Per) 1 and Per 2, in the hypothalamic-pituitary unit while melatonin administration counteracted most of the effects of Cd and augmented hypothalamic Per 2, and adenohypophysial
Per 1 and Per 2 gene expression.