Progesterone receptors are proteins found in various tissues throughout the body, primarily in the uterus, breasts, and ovaries. They play a crucial role in mediating the effects of the hormone progesterone, which is essential for regulating the menstrual cycle, supporting pregnancy, and influencing other reproductive functions. When progesterone binds to these receptors, it triggers a series of cellular responses that help prepare the body for potential pregnancy. This includes thickening the uterine lining and inhibiting further ovulation. Abnormalities in progesterone receptor function can lead to reproductive disorders and are also studied in relation to certain types of breast cancer.