How does heat stress affect prolactin?

Heat stress, such as from sauna use, significantly increases prolactin levels. Prolactin, a hormone produced in the pituitary gland, is known for its role in lactation and other functions like sleep regulation. For example, studies show that men using a sauna at 80 degrees Celsius until exhaustion experienced a tenfold increase in prolactin levels. Similarly, women participating in 20 minutes of dry sauna twice a week had a 510% increase in prolactin levels after each session. These elevated prolactin levels also promote slow wave sleep, the deepest phase of non-REM sleep 1 .

Additionally, prolactin contributes to myelin growth, which increases the efficiency of electrical activity in the brain and aids in repairing nerve cell damage 2 . This highlights the broad impact of heat stress on both physical and cognitive functions through the modulation of prolactin levels.