Oral contraceptive use in women is associated with defeminization of otoacoustic emission patterns.

The production of otoacoustic emissions (OAEs) by the cochlea is a sexually dimorphic trait. Although often hypothesized to be influenced by testosterone in utero, little attention has been devoted to the possibility that levels of circulating sex steroids in adulthood might modulate the sex difference in OAE production. The purpose of the current study was to investigate whether oral contraceptive (OC) use affects OAE production in women, revisiting a question originally posed by McFadden [(2000) Hearing Research 142:23-33]. Forty-five males and 50 females were tested. The women were retrospectively classified based on whether or not they were using OCs at present. Two types of OAEs were quantified: those produced spontaneously (spontaneous otoacoustic emissions or SOAEs) and those produced in response to click stimuli (click-evoked otoacoustic emissions or CEOAEs). Women currently using OCs showed a defeminized pattern of OAE production: they produced fewer SOAEs, SOAEs with significantly less power, and smaller CEOAE response amplitudes compared with naturally cycling women who were tested irrespective of phase of the menstrual cycle. It is proposed that the observed group difference may be mediated by the interaction of circulating estradiol with estrogen receptor alpha (ERα) or estrogen receptor beta (ERβ) receptors in the cochlea.