TY - BOOK AU - Asmaa Mohamed Saad Zaghloul Attaalla AU - Amr Yehia Sakr , AU - Ehab Saad Abdelnaby , AU - Rabab Ahmed Abdelmenem , TI - Incidence and predictive factors of radiotherapy induced hypothyroidism in head and neck cancer patients / PY - 2018/// CY - Cairo : PB - Asmaa Mohamed Saad Zaghloul Attaalla , KW - Head and neck cancer patients KW - Radiotherapy (RT) KW - Radiotherapy induced hypothyroidism N1 - Thesis (M.Sc.) - Cairo University -Faculty of Medicine - Department of Oncology (Clinical); Issued also as CD N2 - Head and neck cancer is the sixth most common cancer in the world.1 Head and neck cancer is predominantly a loco-regional disease, and radiotherapy and surgery are major treatment options². Radiotherapy (RT) with or without chemotherapy is the major treatment modality in locally advanced head and neck (HN) cancer. Despite excellent loco-regional control, RT is often associated with late side effects, including chronic xerostomia, osteoradionecrosis, trismus and fibrosis of the soft tissue. Radiation-related late side effects have become increasingly important in HN cancer, because late side effects may adversely affect the quality of life of cancer survivors.³ The Thyroid gland is the largest endocrine gland in human body. Thyroid hormones are crucial for metabolism, growth and development, energy expenditure, and the function of many organs.⁴ Thyroid gland is one of the most radiosensitive normal tissues in the human body. It is frequently affected by radiotherapy in head and neck patients, and thyroid dysfunctions are commonly seen following irradiation.⁵⁶ Despite improvements in the technique of radiation therapy of the head and neck tumors , its effects on the thyroid gland remain significant, as it is located in very close proximity to the target of treatment. However, hypothyroidism incidence among this populations remains unknown with many cases passing unnoticed.⁷ Untreated hypothyroidism cases are associated with m arked morbidities that may affect their quality of life.⁸ ER -