Physiological and Neurobiological Bases of Age-Related Hearing Loss: Biotherapeutic Implications

Purpose: The aim of this study was to highlight growing evidence of interactions between hormones and the structure and function of the auditory system. Method: Recent studies implicating sex hormones and other natural hormones in the modulation of hearing status in age-related hearing loss were reviewed. Results: Progesterone, a sex hormone, has been shown to have negative effects on the hearing of older women and aging mice, whereas, in contrast, estrogen was found in some cases to have a positive influence. Aldosterone, used in studies of animal models of autoimmune hearing loss, slowed the progression of hearing loss. Follow-up studies in humans revealed that auditory measures varied as serum aldosterone levels shifted within the normal range, in otherwise healthy older subjects. This was true for simple as well as complex auditory tasks (i.e., sound spatial processing), suggesting benefits of aldosterone to postperipheral auditory processing as well. In addition, evidence suggests that this functional hearing improvement occurred in association with anatomical improvements to the stria vascularis-an important site of anatomical change in presbycusis. Conclusions: Audiology is now at the point where the search for biomedical interventions to modulate or prevent age-related hearing loss can move forward. Such interventions would require multidisciplinary collaborative initiatives by researchers in such areas as drug development, anatomy, auditory physiological and perceptual testing, and drug microdelivery systems.