Peat Archive

Ray Peat identified prolactin as an underrecognized stress hormone with wide-ranging harmful effects. While best known for its role in lactation, prolactin is released under stress, darkness, and estrogen exposure, and promotes inflammation, immune dysfunction, and tumor growth. Peat noted that prolactin works synergistically with estrogen and serotonin, forming a self-reinforcing inflammatory cascade.

Peat recommended reducing prolactin through bright light exposure, thyroid support, progesterone, and dopamine-supporting strategies (since dopamine inhibits prolactin). He noted that many of the health benefits attributed to bright light and exercise may work partly through prolactin suppression.