Editing Endocrine system (section)

===Pituitary gland===
The [[pituitary gland]] is formed within the rostral neural plate. The Rathke's pouch, a cavity of ectodermal cells of the [[oropharynx]], forms between the fourth and fifth week of gestation and upon full development, it gives rise to the anterior pituitary gland. By seven weeks of gestation, the anterior pituitary vascular system begins to develop. During the first 12 weeks of gestation, the anterior pituitary undergoes cellular differentiation. At 20 weeks of gestation, the [[hypophyseal portal system]] has developed. The Rathke's pouch grows towards the third ventricle and fuses with the diverticulum. This eliminates the lumen and the structure becomes Rathke's cleft. The posterior pituitary lobe is formed from the diverticulum. Portions of the pituitary tissue may remain in the nasopharyngeal midline. In rare cases this results in functioning ectopic hormone-secreting tumors in the nasopharynx.

The functional development of the anterior pituitary involves [[spatiotemporal]] regulation of transcription factors expressed in pituitary stem cells and dynamic gradients of local soluble factors. The coordination of the dorsal gradient of pituitary morphogenesis is dependent on neuroectodermal signals from the infundibular bone morphogenetic protein 4 (BMP4). This protein is responsible for the development of the initial invagination of the Rathke's pouch. Other essential proteins necessary for pituitary cell proliferation are [[FGF8|Fibroblast growth factor 8]] (FGF8), Wnt4, and Wnt5. Ventral developmental patterning and the expression of transcription factors is influenced by the gradients of BMP2 and [[Sonic hedgehog|sonic hedgehog protein]] (SHH). These factors are essential for coordinating early patterns of cell proliferation.

Six weeks into gestation, the [[Corticotropic cell|corticotroph cells]] can be identified. By seven weeks of gestation, the anterior pituitary is capable of secreting ACTH. Within eight weeks of gestation, [[Somatotropic cell|somatotroph]] cells begin to develop with [[cytoplasmic]] expression of human growth hormone. Once a fetus reaches 12 weeks of development, the thyrotrophs begin expression of Beta subunits for TSH, while [[gonadotrophs]] being to express beta-subunits for LH and FSH. Male fetuses predominately produced LH-expressing gonadotrophs, while female fetuses produce an equal expression of LH and FSH expressing gonadotrophs. At 24 weeks of gestation, prolactin-expressing [[lactotroph]]s begin to emerge.