[Sensitivity of the thyroideal cell to external irradiation]

Evaluation of the variation in thyroid function utilizing 131I uptake in patients exposed to external radiation to the thyroid gland for reasons not related to this gland. The study was initiated with 54 patients who were examined prior to irradiation. They received an average dose of 5.650 r to the gland in a period of 5-6 weeks. Upon completion of the radiation therapy an abrupt drop in the uptake values occurred reaching the hypofunction range and one month later there is a recovery to 80% of the initial level and the value remains stable up to one year. Followed, year after year, a progressive reduction occurs in the uptake value up to a period of 6 years when the 2 surviving patients have returned to the hypothyroid level. The number of patients during the latter years of the study is too low to be statistically significant. The usefulness of this observation is discussed and a comparison is made of the external irradiation effects and the effects of 131I therapy.