As illustrated above, beneath the hypothalamus is the pea-sized pituitary gland.  The pituitary is sometimes referred to as the master hormone because it produces and releases hormones that direct and control many of the activities of the entire endocrine system.  The pituitary in turn receives its instructions from the hypothalamus.  

The tiny pituitary gland actually has two parts that stimulate the production of hormones.  The anterior lobe (front part) produces growth hormones, thyroid-stimulating hormones (TSH), adrenocorticotropin hormones (ACTH), luteinizing hormones (LH), follicle-stimulating hormones (FSH) and prolactin (for stimulation of female milk production).

The posterior lobe (rear part) is not regulated by the hypothalamus, and its hormones are actually produced by the brain but stored in the posterior lobe.  The posterior lobe hormones are vasopressin (an antidiuretic hormone (a hormone reducing water loss through lower urination) and oxytocin, a hormone affecting the actions of the uterus during childbirth and milk production.    


When operating properly, the hypothalamus is monitoring the entire endocrine system.  When it receives a signal that a particular hormone is needed, it releases a hormone that tells the pituitary that it needs to release a hormone to stimulate a specific endocrine gland.  These hormones released by the pituitary are called stimulating hormones.  Once the hypothalamus receives a signal that the hormone levels are correct, the pituitary stops releasing the stimulating hormones.