الفهرس 
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Abstract
Head and neck cancer is the sixth most common type of cancer which is treated either by chemotherapy, surgery, and radiotherapy or a combination between two of them or all of them. While treating head and neck cancer (HNC) region with radiotherapy, radiation Exposure to healthy cells is potential. the thyroid gland is a gland with butterfly-shaped in the front of the neck, under the voice box, that helps in metabolism by continuously releasing the thyroid hormones into the bloodstream to control many body functions like growth.
Therefore, it’s important to identify the induced thyroid abnormalities when radiotherapy applied to children with head and neck cancer (HNC) since they have a low resistance to radiation, therefore it’s a great addition to help to understand the relationship between thyroid hyperthyroidism and ionizing radiation since it’s still poorly understood in the medical field, as well as a great addition to exposure and protection fields since the thyroid is one of the high-risk organ (HRO).
This study aimed to evaluate Radiation-induced thyroid abnormalities during radiotherapy of head-and-neck area cancers in childhood.
The children were divided into two groups:
1- group 1: 20 cancer patients treated with primary or postoperative radiotherapy for various cancers (nonthyroidal) in the head and neck region with normal TSH, T3, and T4 before Radiotherapy.
Then the baseline serum samples were evaluated, and subsequently, blood samples were obtained from each patient at the end of the 10th session, and the end of RT treatment sessions.
2- group 2: 20 healthy donors of matched age and sex as a control group.
from every subject, 3 ml, a Peripheral blood sample will be collected.
Our results showed that:
In comparison with the control group, TSH level was reduced significantly due to irradiation in the within (18–24 Gy) and after (36–60 Gy) groups respectively.
FT4 level was raised significantly in patient groups (before, within, and after). On the other hand, IGF-1, and TPO were declined significantly in the patient groups when compared to the control group.
An insignificant difference was observed in the 5 studied parameters (TSH, FT3, FT4, IGF-1, and TPO) when comparing the three studied patient groups which illustrate that radiation could change these parameters but not immediately after irradiation.
TSH level of the after group (dose from 36 to 60 Grays) showed a significant negative correlation with the D mean and D 50% of the thyroid, while FT4 level showed a positive correlation. Since FT3 didn’t affect, the changes in TSH and FT4 could be due to radiation, not feedback mechanism.
Only TPO is negatively correlated with radiation total dose in the patient group after radiotherapy (received from 36 to 60 Grays)who discovered that thyroid hormones play a role in the regulation of insulin-like growth factor type 1 (IGF-1) expression and that IGF-1 is linked to thyroid function. A total of 86 patients with thyroid dysfunction (43 hyperthyroid and 43 hypothyroid patients) and 17 euthyroid subjects participated in this study. IGF-1 levels in hyperthyroid patients (198.8 17.0 microg/L) were comparable to those in the control group (217.9 20.3 microg/L) (Inukai et al, 1999).
Thyroid peroxidase also called thyroperoxidase (TPO) or iodide peroxidase, is one of the thyroid enzymes, that secreted into the colloid. TPO works to oxidizes the ions of iodide, to create iodine atoms to synthesize T4 and T3 which are known as thyroid hormones. In the human body, thyroperoxidase is called or known as TPO gen. TPO is considered the key to the synthesis of thyroid hormones. Moreover, TPO is stimulated by TSH. Reduced TPO expression, along with the resulting suppression of thyroid hormone synthesis, should help to boost thyroid dysfunction sooner after irradiation. As a result, thyroid function testing seems to be indicated, even early after external radiation therapy of the head and neck area or after whole-body irradiation. TPO antibodies in the blood indicate that thyroid disease is caused by an autoimmune disorder such as Hashimoto’s disease or Graves’ disease. (Inukai et al.,1999)
In autoimmune disorders, the immune system produces antibodies that mistakenly attack the normal and healthy tissue. Inflammation and impaired thyroid function will be a result of the antibodies that target the thyroid gland. The (+) test of TPO is usually seen in people with chronic thyroiditis. The test is additionally positive in lesser numbers of people with other thyroid diseases (Blasko et al., 2000).
About 3 percent of people with a positive TPO Ab test did not complain of any abnormality, However, the presence of TPO antibodies may additionally amplify the risk of chronic thyroid disorders. The chance of having a positive TPO Ab test is greater in females and will increase with age (Blasko et al., 2000). our study did show that TPO level was significantly decreased when compared patient groups (before, within, after) with the control group, but since TSH level only changes after therapy so the change may be due to TSH levels or not, also TPO is negatively significant correlated with radiation total dose in the patient group after radiotherapy (received from 36 to 60 Gy) (p=0.045*).
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