Progesterone receptors mediate genomic and non-genomic actions in human endometrium. Uterine responsiveness to progesterone is dependent on nuclear PRA/B. Progesterone also acts through different membrane-bound PRs that mediate non-genomic activities. In addition to progesterone, nuclear PRA/B has been shown to be under estrogenic control in human and animal uteri. Although the non-genomic effects of membrane-bound PRs in the endometrium are unclear, several studies have suggested that the PRA/B-regulated genes are involved in the regulation of endometrial proliferation. PRA/B, progesterone receptor isoforms A and B.