Prolactin is a polypeptide hormone synthesized and secreted by the anterior pituitary gland, placenta, decidua, and by various immune system cells, such as T cells, B cells, and NK cells. It has many functions, including stimulating mammary glands to produce milk (lactation), stimulating surfactant in the fetal lungs at the end of pregnancy, inducing immune tolerance of the fetus during pregnancy, as well as other immuno-regulatory and reproductive functions, and may also have a role in breast cancer development. Cayman's human Prolactin ELISA Kit is an immunometric (i.e., sandwich) ELISA that can be used to measure prolactin within the range of 0.12-100 ng/ml. This assay offers specific and sensitive analysis of prolactin in human serum and plasma, and has not been validated for other types of samples.