An ultrasensitive assay revealed age-related changes in serum oestradiol at low concentrations in both sexes from infancy to puberty

OBJECTIVE Intensive studies of oestrogen receptors have suggested extragonadal functions of oestrogen. However, the in vivo extragonadal functions of oestradiol remain unclear because of the lack of an adequate assay system at low concentrations. In this study, we assessed the usefulness of a new ultrasensitive assay for children. METHODS Serum oestradiol was measured with an ultrasensitive assay (assayable concentration: 5– 1835 pmol/l: ESTR-US-CT, CIS biointernational, France). Intra- and interassay coefficients of variation at low concentrations (