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Abstract

Background: Radiotherapy is a cornerstone in the treatment of head and neck squamous cell carcinoma (HNSCC), especially following surgical excision. However, its impact on surrounding endocrine structures like the thyroid gland is often overlooked. Radiation-induced hypothyroidism is a frequent and underdiagnosed complication that can negatively affect the long-term quality of life in cancer survivors. Despite this, limited local data is documenting the frequency and predictors of post-radiation thyroid dysfunction in such patients. Objective: To determine the frequency of radiation-induced hypothyroidism in post-surgical patients with oral cavity squamous cell carcinoma undergoing radiotherapy or concurrent chemoradiotherapy. Methodology: This was a descriptive cross-sectional study conducted at the ENT and Head and Neck Surgery Department, Liaquat National Hospital, Karachi, from November 2023 to November 2024. A total of 95 patients with histologically confirmed oral cavity squamous cell carcinoma, who had undergone surgery followed by external beam radiotherapy (30–35 fractions), were enrolled using non-probability consecutive sampling. Patients with pre-existing thyroid disorders or prior neck radiation were excluded. Data including demographics, tumor staging, treatment type, and post-radiation thyroid function (TSH, T3, T4) were collected using a structured proforma. Data were analyzed using SPSS v26 with significance set at p ≤ 0.05. Results: Out of 95 patients, 56.8% were male and 43.2% were female. The mean age was 56.2 ± 9.7 years. Subclinical hypothyroidism was detected in 47.4% of the cohort, while 6.3% developed overt hypothyroidism. A significant association was found between hypothyroidism and bilateral neck radiation (p = 0.032), advanced tumor stage (p = 0.041), and receipt of concurrent chemoradiotherapy (p = 0.028). No statistically significant association was observed with age or gender. Conclusion: A substantial proportion of post-operative head and neck cancer patients develop hypothyroidism following radiation therapy, with subclinical hypothyroidism being most common. Regular screening of thyroid function is essential in this population to enable early intervention and improve rehabilitation outcomes.