Normal anterior pituitary function is under the central control of the hypothalamus and higher centers. Hypothalamic releasing and inhibitory factors are secreted into the capillaries of the hypophysial portal circulation at the median eminence. The neurohypophysis consists of neurons arising from the magnocellular and parvocellular neurons of the supraoptic and paraventricular nuclei. The anatomical relationships of the hypothalamus and surrounding brain structures can be clearly demonstrated on magnetic resonance imaging (MRI) scan. The posterior pituitary (neurohypophysis) characteristically has a high signal on T1-weighted images that is lost in cranial diabetes insipidus (Figure 1.1). Coronal MRI scan (T1-weighted) demonstrating the pituitary gland, hypothalamus, and surrounding structures; scan a is an enlargement of scan b. LV, lateral ventricle; 3rd V, third ventricle; OC, optic chiasm; PS, pituitary stalk; ICA, internal carotid artery; CS, cavernous sinus (includes third, fourth, first and second divisions of fifth and sixth cranial nerves). https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429098260/f7dd27ea-9ce5-4b5c-9b1f-612e605e8546/content/fig1_1.tif"/>