Estrogen Receptor Alpha (ERα) is a protein that binds to the hormone estrogen, playing a crucial role in regulating various biological processes. It is primarily found in tissues such as the breast, uterus, and ovaries, where it influences cell growth, differentiation, and reproductive functions. When estrogen binds to ERα, it activates specific genes that control these processes. This receptor is essential for normal development and function of the female reproductive system, and it is also involved in bone health and cardiovascular function. Abnormal ERα activity can contribute to conditions like breast cancer.