CONCISE PUBLICATIONS Elevation of Plasma Neurophysin in Women on Oral Contraceptives

neurohypophysis was demonstrated by changes in the plasma level of a posterior pituitary protein, neurophysin. Neurophysins are intraneuronal proteins associated with oxytocin and vasopressin. They have been shown to be released into the bloodstream. The resting plasma level of neurophysin in normal nonpregnant women is 0.69 ng/ ml+0.7 SD. In women on oral contraceptives, the plasma level is 6.4 ng/ml+4.2 SD (P < 0.001). Estrogen rather than progesterone causes the elevated neurophysin. The effect is observed within 12-24 h of estrogen administra-tion and disappears 3-11 days after estrogen is dis-continued. The results indicate that oral contraceptives act on the neurohypophysis and that estrogen is a potent phar-macologic stimulus useful in studying synthesis and re-lease of neurophysin