Prolactin is a hormone produced by the pituitary gland that primarily regulates milk production in breastfeeding women. This test measures prolactin levels in the blood and is essential for evaluating reproductive health and pituitary function. Elevated prolactin levels (hyperprolactinemia) can cause various symptoms including galactorrhea (inappropriate milk production), irregular menstrual periods, infertility, and decreased libido. High prolactin levels are commonly caused by pituitary tumors (prolactinomas), certain medications, thyroid disorders, or stress. This test is the first step in evaluating patients with unexplained lactation, menstrual irregularities, or fertility problems. It's also used to monitor treatment for prolactin-secreting pituitary tumors and assess overall pituitary function. Early detection of elevated prolactin can prevent complications like osteoporosis and help restore normal reproductive function.