الفهرس 
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Abstract
Introduction: The thyroid produce significant abnormalities after therapeutic external radiation especially head and neck irradiation. Many growth factors are expressed abnormally in benign and malignant thyroid tumors, in part these alterations are probably secondary events because no structural abnormalities have been detected in the involved genes or the respective chromosomal locations . TSH, EGF and TGF ? and TGF-?1 have an important role in differentiated thyroid cancer cells and metastasis development Aim of the work: is to study the changes of growth factors (EGF, TGF-?1)in head and neck externally irradiated patients and the relation of these changes to the thyroid gland, in part these alterations are probably secondary events because no structural abnormalities have been detected in the involved genes or the respective chromosomal locations . TSH, EGF and TGF ? and TGF-?1 have an important role in differentiated thyroid cancer cells and metastasis development - - Subjects and Methods: The study was conducted on 95 subjects.Two patient groups beside healthy reference group. The first patient group included 60 patients with head and neck non thyroid swellings treated with external irradiation presented in Radiotherapy Department Mansoura University Hospital.Liver function tests, serum creatinine, CBCs.Thyroid function test [TSH (IRMA), FT3, FT4 (RIA), Tg (ELISA)].Serum EGF and TGF-?1 (ELISA). Results: Serum EGF after radiation exposure in the prospective subgroup exhibited two phases, significant increase 3-7 weeks after versus the levels before radiation exposure and then insignificant decrease 3-5 months after exposure.Serum EGF levels in the retrospective subgroup were significantly increase (1-2 years after exposure) as compared with the healthy control group. Moreover, there was significant increase in serum TGF-?1 levels in retrospective cases exposed to 40-65 Gy versus those exposed to30 Gy. Study of patient group with thyroid swellings revealed that the preoperative serum EGF and TGF-?1 levels were insignificantly higher in patients with malignant thyroid swellings as compared with those with benign swellings and healthy control, but there were insignificant decreased levels one week post operative and the follow up of 6/15 cases illustrated that there were insignificant increase in serum levels 3 months post operative. Recurrence of the malignancy was reported in 4/6 of cases.The specificity of EGF in diagnosis of thyroid malignancy was 44.4% with 60% sensitivity. These findings decrease the reliability of serum EGF estimation as biomarkers of thyroid carcinogenesis. Conculsion: EGF and TGF-?1 serum levels showed acute changes following irradiation which normalized several months after.The diagnostic role of serum levels of EGF & TGF- ?1 in thyroid malignancy was neglegable, while its role in follow up could be considered. Recommendation: 1. The interrelationship between the effect of irradiation on growth factors and its role in cancer development potentiates the therapeutic stratgies of anti-growth factors in irradiated patient for more effective irradiation and more protection against the carcinogenic hazards of this irradiation. 2.Follow up of children cases exposed to external irradiation is recommended in further studies, as the thyroid is more sensitive to irradiation in children than adult.