Pituitary gland Rathke's pouch. This contrasts with the posterior pituitary, which originates from neuroectoderm. Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in the hypothalamic capillaries leading to infundibular blood vessels, which in turn lead to a second capillary bed in the anterior pituitary. This vascular relationship constitutes the hypothalamo-hypophyseal portal system. Diffusing out of the second capillary bed, the hypothalamic releasing hormones then bind to anterior pituitary endocrine cells, upregulating or downregulating their release of hormones. The anterior lobe of the pituitary can be divided into the pars tuberalis (pars glandularis) and pars
Pituitary adenoma shown there are to date scant studies – of poor quality – to either support or refute this assumption. Adenomas which exceed in size are defined as "macroadenomas", with those smaller than 10 mm referred to as "microadenomas". Most pituitary adenomas are microadenomas, and have an estimated prevalence of 16.7% (14.4% in autopsy studies and 22.5% in radiologic studies). A majority of pituitary microadenomas often remain undiagnosed and those that are diagnosed are often found as an "incidental finding", and are referred to as "incidentalomas". Pituitary macroadenomas are the most common cause of hypopituitarism, and in the majority of cases