The protective effect of adrenocorticotropic hormone treatment against noise-induced hearing loss

Objective: NIHL is a common problem, and steroids are the most effective treatment option. In this study, we aimed to evaluate the protective effects of the synthetic adrenocorticotropic hormone (ACTH) analogues, which induce endogenous steroid secretion, against noise-induced hearing loss (NIHL) and to compare their effectiveness with that of steroid treatment. Methods: Twenty-four male Sprague Dawley albino rats were divided into four subgroups as follows: group 1 (n = 6) control, group 2 (n = 6) saline, group 3 (n = 6) dexamethasone (2 mg/kg/ day intramuscularly [IM]), group 4 (n = 6) ACTH analogue (0,4 mg/kg/day IM), respectively. Three groups (groups 2-4) were exposed to white noise (105 dB SPL, 12 h). All the rats were evaluated for hearing thresholds of 10 kHz, 20 kHz, and 32 kHz via acoustic brainstem responses (ABR) measurement. After the basal threshold measurements, measurements were repeated immediately after the noise and on day 7 and day 21. Results: Both steroid and ACTH analogue groups showed significantly better hearing outcomes than the saline group on day 7 (p < 0.001) and day 21 (p < 0.001) after the noise exposure. No superior treatment effect was demonstrated in either the steroid or ACTH analogue group. None of the related intervention groups reached the basal hearing thresholds. Conclusion: Steroids were effective drugs for the treatment of NIHL. ACTH analogues also demonstrated promising therapeutic effects for NIHL. Further studies to establish ACTH analogues as an alternative NIHL treatment option to steroids are needed. (C) 2018 Elsevier B.V. All rights reserved.