Evidence for a nonpituitary source of amniotic fluid prolactin

Prolactin levels were determined during a gonadotropin-induced pregnancy following hypophysectomy for a chromophobe adenoma. Maternal plasma prolactin concentrations did not vary significantly from prepregnancy values throughout gestation, remaining between 25 and 35 ng/ml. Fetal prolactin levels were 55 ng/ml and maternal levels were 29 ng/ml at delivery. Amniotic fluid prolactin concentration was approximately 100 ng/ml. Decidual tissue isolated from the maternal surface of the chorion released significant amounts of prolactin into the medium during a 24-hour incubation. Final concentrations of prolactin in the incubation medium were as high as 196 ng/ml. It is concluded that after hypophysectomy (1) prolactin is present in the maternal circulation during pregnancy, and the concentration does not change significantly throughout gestation; (2) fetal and amniotic fluid prolactin concentrations near term do not differ significantly from those reported for normal pregnancy; and (3) the capacity of the decidua to release prolactin in vitro is not diminished compared with normal term decidua, suggesting a nonpituitary source of amniotic fluid prolactin.