Prolactin is a hormone. A hormone is a chemical substance, which is secreted by an endocrine gland, and is transported to another part of the body (the "target tissue") where it has an effect. Hormones act at the target tissue by binding to a receptor site on the responding cells. The body's endocrine system uses hormones to convey information and control many of the day to day functions.
Prolactin is produced primarily in the front part of the pituitary gland. This gland is known as the "master gland" because it controls a range of other endocrine organs. The pituitary gland is about the size of a pea and is situated near the middle of the brain.
Prolactin is produced in both men and women. Prolactin is secreted periodically by the pituitary throughout the day and night. The secretion of prolactin is increased by a number of external stimuli including stress, breast-feeding and sexual activity.
In women, the breast is the predominant prolactin target tissue. Prolactin has the effect of stimulating the breast to produce breast milk in late pregnancy and sustaining milk production after birth. To have this effect on the breast, other hormones such as oestrogen also need to be present.
Prolactin is also normally produced in men but appears to have no specific role in males. High prolactin levels have the effect of suppressing the hormones responsible for the normal functioning of the ovaries and testes.
High prolactin levels can therefore lead to menstrual irregularity and/or fertility problems.
Conditions causing elevated prolactin secretion Hyperprolactinaemia is the term given to having too-high levels of prolactin in the blood.
Conditions causing decreased prolactin Bulimia; Excess of dopamine.
Hyperprolactinaemia (BrE) or hyperprolactinemia (AmE) is the presence of abnormally high levels of prolactin in the blood. In women, a high blood level of prolactin often causes hypoestrogenism with anovulatory infertility and a decrease in menstruation. In some women, mensturation may disappear altogether (amenorrhea). In others, mensturation may become irregular or menstrual flow may change. Women who are not pregnant or nursing may begin producing breast milk. Some women may experience a loss of libido (interest in sex). Intercourse may become painful because of vaginal dryness.
Low prolactin in women: symptoms include lack of milk production, fatigue, and loss of underarm and pubic hair.
