As you know, the hypothalamus is thebasal part of diencephalon, forebrain(Figure 22.1) and it regulates a widespectrum of body functions. It containsseveral groups of neurosecretory cellscalled nuclei which produce hormones.These hormones regulate the synthesis and secretion of pituitaryhormones. However, the hormones produced by hypothalamus are oftwo types, the releasing hormones (which stimulate secretion of pituitaryhormones) and the inhibiting hormones (which inhibit secretions ofpituitary hormones). For example a hypothalamic hormone calledGonadotrophin releasing hormone (GnRH) stimulates the pituitarysynthesis and release of gonadotrophins. On the other hand, somatostatinfrom the hypothalamus inhibits the release of growth hormone from thepituitary. These hormones originating in the hypothalamic neurons, passthrough axons and are released from their nerve endings. These hormonesreach the pituitary gland through a portal circulatory system and regulatethe functions of the anterior pituitary. The posterior pituitary is underthe direct neural regulation of the hypothalamus (Figure 22.2)