title: Incidence of primary hypothyroidism in patients exposed to therapeutic external beam radiation, where radiation portals include a part or whole of the thyroid gland.
abstract: BACKGROUND
  Hypothyroidism is a known consequence of external-beam radiotherapy to the neck encompassing a part or whole of the thyroid gland. In this non-randomized prospective study, we have tried to evaluate the response of the thyroid gland to radiation by assessing thyroid function before irradiation and at regular intervals after irradiation.
  
  
  OBJECTIVE
  THE AIM OF THIS STUDY WERE TO ASSESS IN THE CANCER PATIENTS, WHO WERE EXPOSED TO THE THERAPEUTIC EXTERNAL BEAM RADIATION, WHERE RADIATION PORTALS INCLUDE A PART OR WHOLE OF THE THYROID GLAND: the incidence of primary hypothyroidism, the time required to become hypothyroid, any relation between the total dose for the development of hypothyroidism, and whether there are any patient or treatment-related factors that are predictive for the development of hypothyroidism, including the use of concurrent chemotherapy.
  
  
  METHODS
  This non-randomized, prospective study was conducted for a period of 2 years in which thyroid function was assessed in 59 patients (cases) of head and neck cancer, breast cancer, lymphoma patients and other malignancies, who had received radiotherapy to the neck region. 59 euthyroid healthy patients (controls) were also taken, who had not received the neck irradiation. These patients/controls were assessed periodically for 2 years.
  
  
  RESULTS
  The incidence of hypothyroidism after external beam radiation therapy (EBRT) to neck where radiation portals include part or whole of the thyroid gland was 16.94%, seven cases had subclinical hypothyroidism (11.86%) and three cases had clinical hypothyroidism (5.08%). Mean time for development of hypothyroidism was 4.5 months. There was no effect of age, gender, primary tumor site, radiation dose and chemotherapy, whether neoadjuvant or concurrent with the development of hypothyroidism.
  
  
  CONCLUSIONS
  In summary, we found that thyroid dysfunction is a prevalent, yet easily treatable source of morbidity in patients undergoing radiation therapy to neck where radiation portals include a part or whole of the thyroid gland.
authors.affiliation: Department of Endocrinology, Sher-i-Kashmir Institute of Medical Sciences, Soura, Srinagar, Jammu and Kashmir, India.
authors.forename: B A
authors.initials: BA
authors.lastname: Laway
authors.forename: Kuchay M
authors.initials: KM
authors.lastname: Shafi
authors.forename: Sabiya
authors.initials: S
authors.lastname: Majid
authors.forename: M Maqbool
authors.initials: MM
authors.lastname: Lone
authors.forename: F
authors.initials: F
authors.lastname: Afroz
authors.forename: Showkat
authors.initials: S
authors.lastname: Khan
authors.forename: R
authors.initials: R
authors.lastname: Roohi
keywords: chemotherapy; external beam radiation; head and neck cancer; hypothyroidism
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