Chicken Prolactin (PRL) is a peptide hormone belonging to the prolactin/growth hormone family, which also includes growth hormone (GH) and placental lactogen–related hormones that regulate growth, metabolism, and reproductive physiology. In chickens (Gallus gallus), prolactin is produced primarily by lactotroph cells in the anterior pituitary gland and acts through the prolactin receptor (PRLR), activating intracellular signaling pathways such as JAK2/STAT5 that regulate gene expression and physiological responses. PRL plays a central role in reproductive behavior and parental care, particularly in the regulation of broodiness, where elevated prolactin levels promote nesting behavior, incubation of eggs, and suppression of further egg laying. In addition to its reproductive functions, chicken prolactin influences immune regulation, feather development, and metabolic processes, and is expressed in several tissues including the pituitary, ovary, and immune organs. Because prolactin is a key hormonal regulator of avian reproductive cycles and parental behavior, it is widely studied in poultry science to understand broodiness control, egg production, and endocrine regulation of reproduction, providing insights important for improving reproductive management and productivity in commercial poultry systems.