Dynamic Changes in Free Triiodothyronine (FT3) and Their Correlation with Hearing Recovery in Sudden Sensorineural Hearing Loss: Clinical Implications.

Abstract

Objectives: Sudden sensorineural hearing loss (SSNHL) is a sudden onset condition of unknown etiology, often accompanied by tinnitus and vertigo, significantly affecting patients' quality of life. While some individuals experience spontaneous recovery, the unpredictability of treatment outcomes and potential complications pose clinical challenges. Recent studies suggest a potential link between thyroid hormone levels-particularly free triiodothyronine (FT3) and thyroid-stimulating hormone (TSH)-and both the pathogenesis and prognosis of SSNHL. However, the precise mechanisms remain unclear. This study aims to investigate the correlation between thyroid hormone abnormalities and hearing recovery in SSNHL patients, providing insights to enhance diagnostic and therapeutic approaches.

Methods: This prospective observational study included 66 SSNHL patients admitted to the Affiliated Hospital of Qingdao University between April 2024 and February 2025. Serum TSH and FT3 levels were measured using chemiluminescence immunoassay, while hearing function was evaluated through pure-tone audiometry following standard guidelines. The "post-treatment hearing gap (PTHG)" was introduced as a quantitative measure of treatment efficacy. All patients received comprehensive treatment, including glucocorticoid therapy and hyperbaric oxygen therapy, and were classified into effective and ineffective groups based on hearing recovery outcomes.

Results: No significant differences in gender or comorbidities (tinnitus, ear fullness, dizziness) were observed between the abnormal thyroid function group (n = 45) and the normal thyroid function group (n = 21) (all p > 0.05). Similarly, initial TSH and FT3 levels did not differ significantly among patients with varying degrees of hearing impairment (mild, moderate, severe) (p > 0.05). However, during treatment, ΔFT3 demonstrated a significant negative correlation with PTHG (r = -0.739, p = 0.002), suggesting that a greater increase in ΔFT3 is associated with improved hearing recovery. Additionally, TSH levels showed a significant positive correlation with ΔFT3 (p < 0.05).

Conclusions: Abnormal thyroid function in SSNHL patients was not associated with the severity of hearing loss. However, dynamic changes in FT3 during treatment showed a significant correlation with therapeutic efficacy, suggesting that monitoring ΔFT3 may have clinical value in prognostic assessment. Nonetheless, this study had a limited sample size, and the potential influence of hormone therapy on thyroid function was not accounted for. Therefore, the role of thyroid hormones in SSNHL warrants further validation through large-scale prospective studies and mechanistic investigations.