Mostly, endorphins are the class of hormones from the pituitary gland that interact with the bodies opioid receptors. So the reduction in stress and calming feeling one gets from a hug would mostly be due to endorphins. That said there are non-endorphins at play too most likely. Serotonin is likely involved for example as well.
@freemo @hugbot
Cool thanks. This is why i really like the fedi, you can learn lots of great stuff.