16-Epiestriol is a minor estrogen metabolite and stereoisomer of estriol, exhibiting very weak estrogenic activity. It is primarily utilized as a research reagent in endocrinology to study estrogen receptor binding, selective estrogen receptor modulation (SERM) effects, and metabolic pathways involved in hormone synthesis and degradation. Potential investigational applications include exploring its role in hormone replacement therapy for postmenopausal symptoms (e.g., hot flashes, vaginal atrophy, osteoporosis prevention) and in hormone-sensitive conditions like breast cancer, due to its tissue-selective properties. Not approved for routine clinical use; applications are experimental.