Estrone (E1) is produced in women mainly in the ovary. While a minor female sex hormone, it is one of the three major endogenous estrogens.

In women (or girls) estrone testing may be used to evaluate early onset puberty, investigate menstrual abnormalities, monitor IVF procedures and hormone replacement therapy, and detect estrogen producing tumors. In men estrone tests may be used to diagnose delayed puberty, enlarged breasts