A pea-sized endocrine gland attached by a thin stalk to the hypothalamus at the base of the brain. It consists of two main lobes, the anterior and the posterior, separated in nonhumans by a much smaller intermediate lobe. The anterior pituitary (or adenohypophysis) secretes such hormones as growth hormone, the gonadotrophins, prolactin, thyroid-stimulating hormone, and ACTH. Because these hormones regulate the growth and activity of several other endocrine glands, the anterior pituitary is often referred to as the master endocrine gland. Activity of the anterior pituitary itself is regulated by specific releasing hormones produced by the hypothalamus (see also neuroendocrine system). The posterior pituitary (or neurohypophysis) secretes the hormones oxytocin and antidiuretic hormone, and the intermediate lobe secretes melanocyte-stimulating hormone. In humans the pituitary lacks a functionally discrete intermediate lobe.