Though in literature — fiction and poetry — falling in love and romantic love play a crucial role and several psychosocial conceptions of couple attachment involve the participation of hormones, human endocrinology noticed this theme only marginally. Falling in love shows some signs of hormonal response to stressors with changes in serotonin availability and neurotrophin (transforming growth factor β) concentration, in later phases of love endorfins and oxytocin, may play a role; however, the proof of hormonal events associated with love in humans has been lacking up to now.