Under the beam, beyond the tumor: An observational study of post-radiotherapy hypothyroidism in head and neck cancers

Abstract Background: Hypothyroidism is a frequently under-recognized late complication of radiotherapy (RT) in head and neck cancers. Its insidious onset and vague symptoms often delay diagnosis, affecting long-term quality of life. This study aimed to assess the incidence, timing, and severity of thyroid dysfunction following external beam radiotherapy (EBRT), and to identify correlations with clinical and treatment-related variables. Materials and Methods: A retrospective observational study was conducted on patients with head and neck malignancies treated with curative-intent EBRT using standard fractionation. Patients with preexisting thyroid disease or follow-up 50 years, females, and those receiving bilateral neck RT. A positive but nonsignificant correlation ( r = 0.28) was observed between radiation dose to lower cervical regions and TSH levels. Conclusion: Hypothyroidism is a common sequela of head and neck RT, often subclinical. Routine TSH monitoring starting at 6 months post-RT and annually thereafter is advised, particularly for older patients and those receiving bilateral neck irradiation. Early detection and treatment can improve survivorship and long-term quality of life.