Tumors of the Adenohypophysis

The human pituitary is an oval, bean-shaped, and bilaterally symmetric organ located in the sella turcica, near the hypothalamus and optic chiasm, surrounded by the sphenoid bone, and covered with the sellar diaphragm. It is a composite endocrine organ divided in two parts: the adenohypophysis, which derives from an evagination of stomodeal ectoderm (Rathke pouch), and the neurohypophysis, which arises from the neuroectoderm of the floor of the forebrain. The adult pituitary weighs about 0.6 g and measures about 13 mm transversely, 9 mm anteroposteriorly, and 6 mm vertically. A reduction in weight is evident in old age, and an increase occurs during pregnancy and lactation. Although the pituitary size regresses after cessation of lactation, the reversion is not complete, the gland weighing 1 g or more in multiparous women.