The pituitary gland (hypophysis) is a small gland beneath the brain. It is divided into an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis). Both lobes are connected to and controlled by the hypothalamus, a part of the brain. The anterior pituitary releases six hormones. One of these is growth hormone (somatotropin), which stimulates the growth of bones and acts on other tissues as well. The remainder of the pituitary hormones regulate other glands, including the thyroid, adrenals, gonads, and mammary glands. These hormones are released in response to substances (releasing hormones) that are sent to the anterior pituitary from the hypothalamus. They can be identified by the ending -tropin, as in gonadotropin. The adjective ending is -tropic.
The posterior pituitary releases two hormones that are actually produced in the hypothalamus. These hormones, antidiuretic hormone and oxytocin, are stored in the posterior pituitary until nervous signals arrive from the hypothalamus to trigger their release. Antidiuretic hormone (ADH) acts on the kidneys to conserve water and also promotes constriction of blood vessels. Both of these actions serve to increase blood pressure. Oxytocin stimulates uterine contractions and promotes milk "letdown" in the breasts during lactation.
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