Radiation-Induced Thyroid Disease

Radiation is a mitogen which may cause damage to the cell DNA. When sufficiently severe, the damage may result in cell death. When the damage is less severe, the consequences to the cell depend upon the gene and cell system that are affected. The thyroid gland is particularly sensitive to the effects of radiation and the evidence that radiation may damage the thyroid gland is overwhelming. Both external and internal radiation have been associated with thyroid diseases (cancer and hypothyroidism, with or without thyroid autoimmunity) both in vitro and in vivo. External radiation to the thyroid was first recognized as a cause of thyroid carcinoma in the 1950s, when incidences were found in individuals who had been given radiotherapy during childhood for an enlarged thymus. This chapter takes a look at the numerous studies which have confirmed and extended these initial observations.