Impact of route of administration on genotoxic oestrogens concentrations using oral vs transdermal oestradiol in girls with Turner syndrome.

Common feminizing doses of oral oestradiol for 12 months result in substantial accumulation of unphysiologic, genotoxic oestrogens compared to transdermal oestradiol, expanding concerns about oral oestrogens' first hepatic passage. Further studies assessing long-term risks of these metabolites in women taking different forms of oestrogen are needed.