The effect of the menstrual cycle on evoked otoacoustic efferent suppression
Mahmood, Sally Louay
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The purpose of the study was to investigate the effects of the menstrual cycle on suppression of transient-evoked otoacoustic emissions. Otoacoustic emissions (OAEs) are soft sounds produced by the inner ear that can be measured in the ear canal by a sensitive microphone. OAEs may be present spontaneously or may be evoked by presenting sound(s) to the ear. Presenting a noise (in addition to the eliciting stimulus) to one or both ears during testing typically causes a change in the measured OAE levels. Because the change is most often a decrease in OAE levels, this effect has been termed "suppression." Although OAE suppression is not used routinely in audiometric evaluations, research has indicated potential clinical value for diagnosis of certain pathologies, such as auditory neuropathy (e.g., Starr et al., 1996). However, more information on sources of normal variation in OAE suppression is needed. Little information is available on how the menstrual cycle affects OAE suppression. In the present study, suppression of transient-evoked OAEs (TEOAEs) was investigated. TEOAEs are measured following the presentation of clicks to the ear. Repeated measures of TEOAE suppression were completed on 30 participants divided into three groups: (1) 10 normally-menstruating females who were not taking oral contraceptives, (2) 10 normally-menstruating females who were taking oral contraceptives, and (3) 10 males. Participants were tested on three separate days. Female participants were tested during menstruation, pre-ovulation/mid-cycle and pre-menstruation. An ovulation prediction kit was used by female participants not taking oral contraceptives to aid in estimating the time of ovulation. Male participants were tested at intervals that corresponded in time to those for the female groups. TEOAE suppression did not differ significantly between the three groups or across the three sessions (one menstrual cycle) for any of the groups. Unsuppressed TEOAE levels were also similar between groups and stable across sessions for all groups. The findings suggest that female sex hormones do not affect TEOAE suppression. From a clinical standpoint, these results are fortuitous in that phases of the menstrual cycle would not need to be taken into account when interpreting unsuppressed TEOAE levels or TEOAE suppression results.