Thyroid-Stimulating Hormone and Free Thyroxine Alterations in Subjects with Occupational Hearing Loss

CONTEXT AND AIM: Occupational hearing loss (OHL) is caused by exposure to industrial noise. Alterations in the thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels are related to hearing loss. The purpose of this study is to investigate the TSH and FT4 level alterations in OHL. METHODS AND MATERIAL: Among 428 subjects, 144 male workers with normal hearing (NH), noise-induced hearing loss (NIHL), and high tone loss (HTL) (N = 48 in each group) were included in this study. All the subjects had normal TSH and FT4 levels. RESULTS: The TSH level is higher in the HTL and NIHL groups in comparison to NH, but it is only significant in the HTL group. The FT4 level is significantly lower in the NIHL group; however, the lower FT4 level in the HTL group is not significant when compared to the NH group. DISCUSSION: The NIHL group may turn into the HTL group over time. This process could be monitored by alteration in their TSH and FT4 levels. CONCLUSIONS: Alterations in the TSH and FT4 levels could be considered as a pathophysiology for OHL. More research is required to investigate the electrophysiological, physiological, and histological correlations of TSH and FT4 and different types of hearing loss caused by noise exposure.