I've read that stress can cause high prolactin , but i don't know the mechanism .can you explain to me , doctors?

Minor mystery: I've known ever since residency that the mere stress of a venipuncture can cause an elevated "spot" prolactin, requiring that it be confirmed with suppression or other testing. Since prolactin is produced in response to factors from the brain over moments, it's in the brain wiring -- like the production during orgasm, nipple stimulation, or sleep. Anybody else know more? Thanks.