Afterwards, each participant was blindly assigned to one of three test groups. In this study, levels of progesterone were sampled and measured in 59 males. Translation: It’s part of the chemical reason why humans develop friendships. Similar to oxytocin, progesterone is partly responsible for the formation of social bonds in mammals. Much of this to do with a hormone called progesterone, a brain chemical that is produced in the pituitary gland and present in both women and men.
