Activity of Progesterone in Spayed Females Not Pretreated with Estrin. ∗

Summary

Experiments in spayed rats indicate that daily administration of 15 mg of progesterone produces progestational changes in the endometrium vaginal mucification and mammary gland development similar to that seen in late pregnancy. It is concluded that, contrary to the generally accepted conception, progesterone can exert all its characteristic actions in spayed females without sensitization by estrogens.