Prolactin is a hormone that affects many different hormones in the body. Present in both men and women, it rarely causes problems, but those who are serious about their health should understand what it is and how it impacts the body’s overall health and well-being. Prolactin, as its name implies, is a hormone that promotes lactation (breast milk production) in mammals and is responsible for a number of other functions and systems. Prolactin is created in the front portion of the pituitary gland in your brain, as well as in the uterus, brain, breasts, prostate, adipose tissue, skin, and immune cells. Prolactin is released when a newborn baby suckles at his/her mother's breast, causing the production of milk. However, this is just the primary and most well-known purpose of prolactin. Prolactin function is still being studied, but research seems to show a variety of purposes for this hormone. For instance, it also regulates behavior, the immune system, metabolism, reproductive systems, and many different bodily fluids. This makes it a crucial hormone for overall health and well-being, for both men and women. Production of prolactin is controlled by two main hormones: dopamine and estrogen. These hormones send a message to the pituitary gland primarily indicating whether to begin or cease the production of prolactin. Dopamine restrains the production of prolactin, while estrogen increases it. For most people, prolactin does its job without a problem, and few are aware of the impact it has on their health. Yet some people can struggle with prolactin levels, which can cause a variety of problems. Too much prolactin in the blood causes hyperprolactinemia, a condition that can lead to menstrual disturbances, estrogen deficiency and testosterone deficiency. High prolactin levels also can cause unwanted lactation. This often occurs during pregnancy or when the thyroid is not functioning properly. Pituitary tumors, known as prolactinomas, and medications that reduce dopamine can also lead to increased prolactin levels. High levels of prolactin are linked to sexual problems. Some of these conditions can be treated with medications that mimic the action of dopamine.It's also possible to have too little prolactin, a condition known as hypoprolactinaemia. This is extremely rare, but it can occur if people have under-active pituitary glands. This is commonly noticed in women after pregnancy who are not able to produce sufficient milk. No other proven health effects of low prolactin levels have been noted. Research is underway to determine if those with low prolactin levels suffer from a reduction in immune system responses.