Concentrations of 2-hydroxyoestrogens in human sera measured by a heterologous immunoassay with an 125I-labelled ligand

A heterologous immunoassay for 2-hydroxyoestrogens1 has been established in which antibodies raised against 2-hydroxyoestradiol-17-succinyl-BSA serve as binding protein and 2-hydroxyoestrone-17-cmo-[125I]iodohistamine as radioligand. Lipophilic serum components competing for binding sites in this system were defined as 'total 2-hydroxyoestrogens'. The underlying assumption of specificity was supported by the pattern of cross-reactivity evaluated with structural related steroids and o-diphenols and by the fact, that an additional chromatography of the serum extracts preceding the competing reaction had little if any effect. Sensitivity: 2.8 ± 1 pg/tube; accuracy: Y = 0.91x + 2.2; r = 0.989; precision: 5.8% intra-assay; 6.5% inter-assay. The following concentrations ( ± standard deviation) were found in the sera of healthy subjects. Young men: 29 ± 5 pg/ml (n = 11); women follicular phase: 32 ± 8 pg/ml (n = 25); luteal phase: 53 ± 13 pg/ml (n = 23); postmenopausal women: 13 ± 4 pg/ml (n = 10); pregnant women 11th–20th week: 70 ± 16 mg/ml (n = 64); 36th–40th week: 240 ± 23 pg/ml (n = 40); newborn cord blood: 604 ± 43 pg/ml (n = 48).