title: Evaluation of thyroid disorders during head-and-neck radiotherapy by using functional analysis and ultrasonography.
abstract: OBJECTIVE
  To evaluate thyroid function and vascular changes during radiotherapy for patients with head and neck cancer.
  
  
  METHODS
  Fifty patients treated with primary or postoperative radiotherapy for various cancers in the head and neck region were prospectively evaluated. The serum samples (triiodothyronine [T3], thyroxine [T4], thyroid-stimulating hormone [TSH], free triiodothyronine [FT3], and free thyroxine [FT4]), the echo level of the thyroid gland, and color Doppler ultrasonography (CDU) parameters of the right inferior thyroid artery (RITA) of the patients were measured before and at regular intervals during radiotherapy. The thyroid gland dose-volume histograms of the patients were derived from their computed tomography-based treatment plans.
  
  
  RESULTS
  There was a significant fall in TSH level (p < 0.0001) but an increase in FT4 (p < 0.0001) and T4 (p < 0.022) levels during the radiotherapy course. The threshold dose required to produce significant changes was 12 Gy (Biologically Effective Dose in 2-Gy fractions, BED(2)). There were significant rises in the patients' pulsatility index, resistive index, peak systolic velocity, blood volume flow levels, and RITA diameter (p < 0.0001), as detected by CDU during radiotherapy, compared to those parameters measured before the treatment. Hypoechogenicity and irregular echo patterns (p < 0.0001) were seen during radiotherapy compared to those before treatment. There was significant Pearson's correlation between the CDU parameters and T4, FT4, and TSH levels.
  
  
  CONCLUSIONS
  Radiation-induced thyroiditis is regarded as primary damage to the thyroid gland. Thyroiditis can subsequently result in hypothyroidism or hyperthyroidism. Our results demonstrated that changes in thyroid vessels occur during radiotherapy delivered to patients. Vessel changes also can be attributed to the late effect of radiation on the thyroid gland. The hypoechogenicity and irregular echo patterns observed in patients may result from the increase in intrathyroidal flow.
authors: Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
authors: Mohsen
authors: M
authors: Bakhshandeh
authors: Bijan
authors: B
authors: Hashemi
authors: Seyed Rabie
authors: SR
authors: Mahdavi
authors: Alireza
authors: A
authors: Nikoofar
authors: Hamid Reza
authors: HR
authors: Edraki
authors: Anoshirvan
authors: A
authors: Kazemnejad
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001158:Arteries / Q000000981:diagnostic imaging; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011832:Radiation Injuries / Q000150:complications; D011879:Radiotherapy Dosage; D013961:Thyroid Gland / Q000098:blood supply / Q000000981:diagnostic imaging / Q000378:metabolism / Q000528:radiation effects*; D013966:Thyroiditis / Q000097:blood / Q000000981:diagnostic imaging / Q000209:etiology*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D018615:Ultrasonography, Doppler, Color
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine