Estrogen receptor beta: re-evaluation of estrogen and antiestrogen signaling.

Estrogen is of vital importance for the development and control of reproductive functions. Until recently, estrogen was believed to regulate complex programs of gene expression by binding to an unique nuclear receptor belonging to the superfamily of ligand-dependent transcription factors. However, the identification of a second estrogen receptor, referred to as ER beta, is leading to a re-evaluation of estrogen signaling and physiology.