Pituitary gland.
Prolactin is a hormone produced by your pituitary gland which sits at the bottom of the brain. Prolactin causes breasts to grow and develop and causes milk to be made after a baby is born. Normally, both men and women have small amounts of prolactin in their blood. Prolactin levels are controlled by other hormones called prolactin inhibiting factors (PIFs), such as dopamine. Prolactin is a single-chain protein hormone closely related to growth hormone. It is secreted by so-called lactotrophs in the anterior pituitary. It is also synthesized and secreted by a broad range of other cells in the body, most prominently various immune cells, the brain and the decidua of the pregnant uterus. Prolactin is synthesized as a prohormone. Prolactin (PRL), also known as luteotropic hormone or luteotropin, is a protein that in humans is best known for its role in enabling female mammals to produce milk; however, it is influential over a large number of functions with over 300 separate actions of PRL having been reported in various vertebrates. Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation, and nursing. Prolactin is secreted in a pulsatile fashion in between these events. Prolactin also plays an essential role in metabolism, regulation of the immune system, and pancreatic development. Prolactin is a hormone produced by your pituitary gland which sits at the bottom of the brain. Prolactin causes breasts to grow and develop and causes milk to be made after a baby is born. Normally, both men and women have small amounts of prolactin in their blood. Prolactin levels are controlled by other hormones called prolactin inhibiting factors (PIFs), such as dopamine. Prolactin is a hormone produced by the anterior portion of the pituitary gland, a grape-sized organ found at the base of the brain. Normally present in low amounts in men and non-pregnant women, prolactin's primary role is to promote lactation (breast milk production).  Prolactin. Guide. A prolactin test measures the level of the hormone prolactin, which is made by the pituitary gland, in your blood. Pregnant women have high levels of prolactin, which helps make breast milk. During pregnancy, prolactin levels increase by 10 to 20 times. After the baby is born, prolactin stays high if you are breast-feeding. In women who do not breast-feed, prolactin levels return to normal soon after they give birth. Results. A prolactin test measures the level of the hormone prolactin, which is made by the pituitary gland, in your blood. Prolactin levels are different throughout the day. The highest levels occur during sleep and shortly after you wake up.  This test measures the level of prolactin in your blood. Prolactin is a hormone made by the pituitary gland, which is in your brain. In women who are pregnant, prolactin stimulates the breasts to make breast milk. If the prolactin-producing cells in your pituitary gland begin to mutate and grow out of control, they can form tumors called prolactinomas. 
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what is prolactin made of