Estrogen 2-, 4-, 6- or 16-hydroxylation by human follicles shown by gas chromatography-mass spectrometry associated with stable isotope dilution.

Follicular fluid, obtained by aspiration of human Graafian follicles in cycles stimulated by clomiphene and hMG + hCG, was analyzed for estrogen content. Carefully controlled extraction and efficient preliminary chromatographic separations were set up. Deuterium labelled analogues were used as internal standards for the quantitative determination by gas chromatography-mass spectrometry and some new derivatives were included in the identification procedure. The identified estrogens and their mean concentrations (ng/ml) are: 2-hydroxy-estrone (0.14), 4-hydroxy-estrone (0.12), 2-hydroxy-estradiol (0.36), 4-hydroxy-estradiol (0.34), 6 alpha-hydroxy-estradiol (13.2), 6 beta-hydroxy-estradiol (6.40), 2-methoxy-estrone (0.83), 2-methoxy-estradiol (10.5), 16-oxo-estradiol (0.41), estriol (10.2), estradiol-17 beta (1365), estradiol-17 alpha (1.91), estrone (211). Metabolism of estradiol by 6-hydroxylation seems to be predominant in the human ovary. The other data suggest that 2-hydroxylation, with subsequent O-methylation, and 16-hydroxylation may be by equivalent pathways, since the sum of the 2-methoxy-estrone and 2-methoxy estradiol concentrations is rather similar to the estriol concentration. Hence, the latter three compounds and the 6-hydroxy-estradiols may be end-products of follicular estrogen metabolism. Catechol estrogen formation by 2-hydroxylation and 4-hydroxylation is shown to be of equal importance in the ovary. These results confirm the presence in the human follicle of various competing estrogen hydroxylases and catechol-O-methyltransferase.