Prolactin is a hormone secreted by the pituitary gland in both men
and women. In women, it prepares breasts to produce milk (lactate). In men,
prolactin's function is not well understood.
In a lactating woman, more prolactin is produced when her breasts
are emptied frequently, resulting in more milk production. Less frequent
emptying of the breasts reduces the amount of prolactin produced, which in turn
reduces the milk supply. Above-normal prolactin levels in women can cause
ovulation to stop.
Above-normal levels of prolactin can indicate a problem with the
pituitary gland that may affect reproductive functions.