Sex Differences in Susceptibility and Resistance to Noise- Induced Hearing Loss in Chinchillas.

There is tremendous variability in the amount of hearing loss individuals develop from a given noise exposure. The reasons for individual differences in susceptibility to noise-induced hearing loss (NIHL) are largely unknown, but may include factors such as levels of endogenous antioxidant enzymes or steroid hormones. Our experiments are focusing on the effects of steroid hormones on susceptibility to NIHL in chinchillas. Chinchillas treated with 17-Beta-estradiol prior to noise exposure developed less permanent hearing loss than controls. The protective effects of estradiol were found in two separate experiments, one utilizing a continuous noise (octave band noise with a center frequency of 4 kHz, at 105 dB SPL for 4 hours), and the other an impulse noise simulating M16 rifle fire. These experiments support the hypothesis that endogenous levels of estrogen could influence individual susceptibility to NIHL.