Prolactin is a peptide hormone involved in lactation, reproductive physiology, immune communication, parental behavior signaling, and regulation of mammary gland development. Although most widely recognized for its role in milk production, prolactin also participates in numerous endocrine and metabolic pathways affecting reproduction, immunity, and tissue adaptation.
The hormone stimulates mammary gland maturation, supports milk synthesis after childbirth, influences reproductive signaling pathways, and contributes to immune-cell communication and osmoregulatory adaptation. Prolactin also participates in behavioral and neuroendocrine pathways associated with maternal physiology and reproductive endocrine balance. Through these actions, it coordinates communication between the pituitary gland, reproductive tissues, mammary glands, and immune systems.
Prolactin is produced mainly by lactotroph cells within the anterior pituitary gland. Smaller amounts may also be synthesized in reproductive tissues, immune cells, and additional endocrine-responsive organs for local signaling functions.
Production rises substantially during pregnancy and lactation in response to estrogen signaling and neural stimulation associated with infant suckling. Pituitary secretion occurs in pulsatile patterns influenced by circadian rhythms, stress physiology, and reproductive endocrine pathways.
Prolactin secretion is regulated primarily by hypothalamic dopamine signaling, which tonically suppresses release under baseline conditions. Reduced dopamine inhibition strongly stimulates secretion. Estrogen signaling, suckling-associated neural pathways, stress physiology, and sleep patterns also influence production dynamics.
The hormone acts through prolactin receptor systems linked to JAK-STAT signaling pathways regulating mammary development, milk synthesis, reproductive signaling, and immune communication. Feedback systems involving dopamine pathways help stabilize circulating concentrations. Through these integrated endocrine signaling systems, prolactin coordinates lactation physiology, reproductive adaptation, mammary gland function, and neuroendocrine communication.
Prolactin supports milk production and broader endocrine-metabolic coordination.
