Possible placental origin of ACTH in normal human pregnancy

IT is well known that the free fraction of plasma cortisol is increased in pregnancy 1 , but it has not been established whether this is a result of maternal pituitary or placental adrenocorticotrophic hormone (ACTH) secretion. Maternal plasma ACTH levels in human pregnancy have been variously reported as elevated 2 , or depressed 3 ; but there is no information on the relationship between ACTH levels and the stage of gestation. We now report that maternal ACTH levels increase progressively throughout pregnancy, that urinary free cortisol levels are raised and show resistance to suppression by dexamethasone and we present evidence suggesting that ACTH may be produced by the placenta.