Cleaved prolactin: evidence for its occurrence in human pituitary gland and plasma.

A form of PRL that is cleaved in its large disulfide loop has been reported in rat and mouse pituitary glands, but it is not known whether it exists in the human pituitary gland and whether it circulates in blood. Recently, we developed an immunoelectrophoretic technique which is capable of measuring immunoreactive variants of PRL and other hormones in plasma. We describe here detection of cleaved PRL in normal and tumor pituitary tissue from a prolactinoma patient and in the plasma of pregnant women.