What causes a rise in prolactin levels (other than medications)?

Elevated prolactin: Besides certain medications, an elevated prolactin can be caused by pregnancy, nursing, liver disease, kidney disease and hypothyroidism. Also seen with significant nipple stimulation (sex, jogging). And then of course pituitary tumors. A pituitary tumor usually causes a significant elevation (>100). These tumors can be very small. Mild elevations of prolactin may not need treatment.