Donatella Marazziti of the University of Pisa in Italy found that new lovers adjust their testosterone to more closely match each other.
“[M]en and women in love have considerably higher levels of the stress hormone cortisol.”
“Men who were in love had lower levels of the male sex hormone testosterone – linked to aggression and sex drive – than the other men. Love-struck women, in contrast, had higher levels of testosterone than their counterparts”
“[W]hen people look at their lovers, the neural circuits that are normally associated with critical social assessment of other people are suppressed”