Prolactin, psychological stress and environment in humans: adaptation and maladaptation.

Non-puerperal lactation and/or hyperprolactinemia in humans have been related to psychological variables in a variety of ways: (1) Non-puerperal nursing; (2) Pseudopregnancy; (3) Rapid weight gain; (4) Psychogenic galactorrhea; (5) Acute prolactin responses to psychological stress; (6) High prolactin levels in persons who cope passively in real life stress situations; (7) Paternal deprivation in women with pathological hyperprolactinemia; (8) Clinical onset of prolactinomas following life-events. Publications on the above subjects are scattered in the literature as curiosities, anecdotal case-reports or unexplained associations, as there is no theoretical frame of reference to accommodate them. We propose that prolactin is a component of a biological, "maternal", subroutine, adaptive to the care of the young, which promotes accumulation of fat for the extraordinary expenses of pregnancy and lactation, the production of milk and maternal behavior. In an attempt to characterize the stimuli responsible for the activation of the maternal subroutine in the absence of pregnancy we studied the hormonal profiles of female volunteers during three types of sessions under hypnosis: (1) Relaxation-only, control sessions; (2) Sessions in which a fantasy of "nursing" was induced; (3) Sessions of evocations of memories. Prolactin surges were related to the evocation, with rage, of humiliating experiences, but not with the fantasy of nursing. Cortisol surges were related to surprise and shock and were negatively associated with prolactin. In conclusion--Prolactin and cortisol are measurable markers of two different, and alternative, coping strategies to "psychological stress".