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Title: In vivo conversion of norethisterone to ethynyloestradiol in perimenopausal women. Author: Reed MJ, Ross MS, Lai LC, Ghilchik MW, James VH. Journal: J Steroid Biochem Mol Biol; 1990 Oct; 37(2):301-3. PubMed ID: 2268563. Abstract: The extent to which norethisterone is converted to ethynyloestradiol is controversial. To investigate the conversion of norethisterone to ethynyloestradiol we have used a double isotope infusion technique to measure the conversion in vivo. The use of acids or bases was precluded to prevent possible artefactual formation of phenolic metabolites of norethisterone. Transfer constants for the conversion of norethisterone to ethynyloestradiol in two perimenopausal women were 2.26 and 2.34% as measured in blood and 2.27 and 0.38% in urine. Results from this study show that a small but significant proportion of norethisterone is converted to ethynyloestradiol in vivo.[Abstract] [Full Text] [Related] [New Search]