Overview
The pituitary gland links the nervous and endocrine systems: the hypothalamus controls the anterior lobe through releasing and inhibiting hormones and the posterior lobe through neurons. This topic covers the hormones of both lobes and how their secretion is controlled.
Hypothalamic-pituitary system
The pituitary gland (also called the hypophysis) sends signals to other glands in the endocrine system. It produces many hormones, many of which stimulate the production of other hormones from other endocrine glands. The pituitary gland is controlled by the hypothalamus, which sits directly above it. The pituitary gland is divided into anterior and posterior lobes. The anterior pituitary is the primary hormone-producing aspect, and is under neuroendocrine control, while the posterior pituitary produces only oxytocin and vasopressin (ADH) and is under direct neural control.
The hypothalamus and anterior pituitary are linked directly by the hypothalamic-hypophysial portal blood vessels, which provide most of the blood supply of the anterior lobe. Hypothalamic-releasing hormones and release-inhibiting hormones are synthesized in the cell bodies of hypothalamic neurons and travel down the axons of these neurons to the median eminence of the hypothalamus. Upon stimulation of these neurons, the hormones are secreted into the surrounding hypothalamic tissue and enter the nearby capillary plexus, which drains into the hypophysial portal vessels and is delivered directly to the anterior lobe of the pituitary. There, the hypothalamic hormones act on the cells of the anterior lobe, where they stimulate or inhibit the release of the anterior pituitary hormones.