The effects of radiation on the thyroid gland: a quantitative analysis.

Radiation can cause cancer of the thyroid, and the thyroid is one of the most radiosensitive tissues. Children are much more sensitive to thyroid irradiation than are adults. The effectiveness of thyroid iodination from radioisotopes of iodine is largely a function of the half-life of the isotope. Short-lived isotopes (132I), which give a high dose rate, are essentially equivalent, rad for rad, to x-irradiation. Long-lived isotopes (131I) are one-fifth or less as effective as x-ray. Stimulation of the thyroid by TSH markedly increases the carcinogenic potential of thyroid irradiation, and inhibition of TSH stimulation probably decreases the carcinogenic effects of radiation.