Hancock S L, McDougall I R, Constine L S
Department of Radiation Oncology, Stanford University School of Medicine, CA 94305, USA.
Int J Radiat Oncol Biol Phys. 1995 Mar 30;31(5):1165-70. doi: 10.1016/0360-3016(95)00019-U.
The thyroid gland is the largest pure endocrine gland in the body and one of the organs most likely to produce clinically significant abnormalities after therapeutic external radiation. Radiation doses to the thyroid that exceed approximately 26 Gy frequently produce hypothyroidism, which may be clinically overt or subclinical, as manifested by increased serum thyrotropin and normal serum-free thyroxine concentrations. Pituitary or hypothalamic hypothyroidism may arise when the pituitary region receives doses exceeding 50 Gy with conventional, 1.8-2 Gy fractionation. Direct irradiation of the thyroid may increase the risk of Graves' disease or euthyroid Graves' ophthalmopathy. Silent thyroiditis, cystic degeneration, benign adenoma, and thyroid cancer have been observed after therapeutically relevant doses of external radiation. Direct or incidental thyroid irradiation increases the risk for well-differentiated, papillary, and follicular thyroid cancer from 15- to 53-fold. Thyroid cancer risk is highest following radiation at a young age, decreases with increasing age at treatment, and increases with follow-up duration. The potentially prolonged latent period between radiation exposure and the development of thyroid dysfunction, thyroid nodularity, and thyroid cancer means that individuals who have received neck or pituitary irradiation require careful, periodic clinical and laboratory evaluation to avoid excess morbidity.
甲状腺是人体最大的纯内分泌腺，也是治疗性外照射后最易出现具有临床意义异常的器官之一。甲状腺所接受的辐射剂量超过约26 Gy时，常常会导致甲状腺功能减退，其可能为临床显性或亚临床性，表现为血清促甲状腺素升高而血清游离甲状腺素浓度正常。当垂体区域接受常规1.8 - 2 Gy分割剂量超过50 Gy时，可能会出现垂体或下丘脑性甲状腺功能减退。甲状腺的直接照射可能会增加格雷夫斯病或甲状腺功能正常的格雷夫斯眼病的风险。在具有治疗相关性的外照射剂量后，已观察到寂静性甲状腺炎、囊性变、良性腺瘤和甲状腺癌。甲状腺的直接或间接照射会使分化良好的乳头状和滤泡状甲状腺癌的风险增加15至53倍。甲状腺癌风险在年轻时接受辐射后最高，随治疗时年龄增加而降低，并随随访时间延长而增加。辐射暴露与甲状腺功能障碍、甲状腺结节和甲状腺癌发生之间可能存在较长的潜伏期，这意味着接受颈部或垂体照射的个体需要进行仔细的定期临床和实验室评估，以避免过多的发病情况。
