الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The effects of radiation exposure on the thyroid gland varies from transient thyroiditis, to sub-clinical radiation induced hypothyroidism (RIHT), clinical RIHT, or malignant thyroid neoplasms. RIHT has the clinical presentation of primary hypothyroidism. Clinical diagnosis is based on laboratory testing of TSH and fT4. Subclinical RIHT occurs with increased TSH in absence of clinical symptoms and/or normal fT4. Clinical RIHT occurs with presence of clinical classic hypothyroid symptoms. Radiological findings of RIHT include shrinking size, heterogenicity, altered vascularity, nodule formation and capsular infiltrates. However, the most prominent finding is shrinking size. This study was conducted to assess the threshold predictors of RIHT. We have completed 2 years of follow up to 50 patients with different malignancies who were treated by radiotherapy to the neck. Baseline assessment of the thyroid laboratory and radiologically was done prior to the start of radiotherapy. Periodic testing of the cohort through the follow up period was done by clinical examination, measurement of TSH, fT4 and thyroid ultrasonography.