progesterone receptor (PR)

The progesterone receptor (PR) is a protein found inside certain cells that detects and responds to the hormone progesterone. Progesterone is important for regulating the menstrual cycle, supporting pregnancy, and maintaining reproductive health. When progesterone binds to the PR, it activates the receptor, which then influences gene expression—turning certain genes on or off—to support processes like preparing the uterus for pregnancy. The presence or absence of the PR in tissues, such as breast or ovarian tissue, helps doctors understand hormone-related conditions and guide treatments for hormonal imbalances or cancers.