Estetrol (E4) is a naturally occurring estrogenic steroid hormone produced exclusively during pregnancy by the fetal liver. It is classified as a selective estrogen receptor modulator (SERM) with distinct receptor selectivity and biological activity compared to other estrogens.

This compound is widely used in biochemical, pharmacological, and endocrinology research to study estrogen receptor signaling, hormone metabolism, and receptor selectivity. Estetrol demonstrates differential binding affinity for estrogen receptor subtypes, making it valuable for mechanistic studies involving hormonal regulation, reproductive biology, and drug development.

With high purity (≥98% by HPLC), estetrol is suitable for use in analytical techniques such as HPLC, as well as in cell-based assays and receptor-binding studies. It is commonly utilized in academic research, pharmaceutical development, and natural product investigations focused on steroid hormones and endocrine function.