Estrogen Replacement Reduces Hearing Threshold Shifts and Cochlear Hair Cell Loss After Acoustic Overexposure in Ovariectomized Rats

Abstract

Objectives. The relationship of estrogen (the primary female sex hormone) with hearing function has been studied in both humans and animals. However, whether estrogen levels affect hearing remains uncertain. Therefore, in this study, we investigated changes in the vulnerability of hearing to acoustic overexposure in ovariectomized female rats. Methods. Eighteen 8-week-old female Sprague-Dawley rats were separated into four groups as follows: sham ovariectomy (OP), OP only, and OP treated with low (10 µg/kg) or high doses (100 µg/kg) of estrogen. Rats in the estrogen replacement groups were given two intraperitoneal injections. Hearing thresholds were measured before noise exposure, and at 1 day and 2 weeks after exposure. Results. The hearing thresholds of the sham OP and OP-only groups were not significantly different. However, both estrogen groups showed a lower threshold shift than the OP-only group. Histological immunostaining analyses showed that hair cell loss in the 32 kHz region was more severe in the sham OP group than in the OP-only group. Furthermore, there was little or no hair cell loss in either estrogen replacement group and significantly more hair cell loss in the OP-only group. Conclusion. These results suggest that estrogen replacement may reduce the vulnerability of hearing to noise exposure in menopausal women.

Sex differences in associated factors for age-related hearing loss

“…In the multiple analysis for females, the OR for age at menarche yielded statistical significance, with an OR of 1.119 ( P = .006). This finding may suggest a reduced risk of ARHL associated with early estrogen exposure, aligning with previous research indicating estrogen’s protective role in hearing preservation [ 38 , 39 ]. However, it’s notable that while age at menarche was included as a variable, the duration of hormone exposure was excluded from the model.…”

Effects of Androgen Receptor Inhibition on Kanamycin-Induced Hearing Loss in Rats

“…The otoprotective effects of estrogen have been reported and are found to be transduced through multiple estrogen receptors [ 15 ]. Additionally, estrogen replacement therapy reportedly prevented noise-induced hearing loss in ovariectomized rats [ 16 ].…”

Telmisartan Attenuates Kanamycin-Induced Ototoxicity in Rats

“…Thus, one of the therapeutic strategies against aminoglycoside-induced ototoxicity has targeted inflammatory responses and oxidative stresses in the cochlea [ 21 ]. A number of antioxidant molecules—such as dihydromyricetin, nuclear factor erythroid-2-related factor 2, and avocado oil extract—have been reported to have protective effects against oxidative stress and inflammatory conditions and aminoglycoside-induced ototoxicity [ 22 , 23 , 24 , 25 , 26 , 27 ]. However, few therapeutic agents are clinically available for aminoglycoside-induced ototoxicity.…”