Division of Nuclear Medicine, Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
Clin Nucl Med. 2011 Oct;36(10):899-903. doi: 10.1097/RLU.0b013e31821a2751.
Following thyroidectomy, a patient with papillary thyroid carcinoma was found to have widespread radioiodine-avid metastatic lesions and was treated with I-131. When follow-up scanning was anticipated, his 24-hour urinary iodine was found to be 254 μg. Because of the interim development of moderate renal failure, he was considered to be a candidate for preparation using recombinant human thyroid-stimulating hormone (rhTSH), with continued administration of thyroid hormone. To decrease the dilution effect of nonradioactive iodine, levothyroxine was replaced with liothyronine, with a resultant decrease in 24-hour urinary iodine to less than 110 μg, followed by radioiodine imaging, dosimetry, and retreatment with I-131 for persistent, though improved disease. The dilution of radioiodine with nonradioactive iodine from any source may degrade image quality and reduce the effectiveness of therapy. The use of rhTSH has advantages in the evaluation and I-131 treatment of differentiated thyroid cancer. There is evidence that this approach results in a longer effective half-time of radioiodine in remnants, improved bone marrow dosimetry, and comparable remnant ablation efficacy as compared with hormone withdrawal. However, it entails continued administration of thyroid hormone, which is a source of nonradioactive iodine. Reduction of the nonradioactive iodine burden of levothyroxine by conversion to liothyronine warrants investigation as possibly enhancing the advantages of rhTSH.
患者在甲状腺切除术后发现有广泛的放射性碘-131 摄取转移病灶，随后接受了 I-131 治疗。在进行随访扫描时，发现其 24 小时尿碘为 254μg。由于中期出现中度肾功能衰竭，他被认为适合使用重组人促甲状腺激素（rhTSH）进行准备，同时继续服用甲状腺激素。为了减少非放射性碘的稀释效应，将左甲状腺素替换为三碘甲状腺原氨酸，导致 24 小时尿碘降至 110μg 以下，随后进行放射性碘成像、剂量测定，并再次用 I-131 治疗持续存在但改善的疾病。来自任何来源的非放射性碘对放射性碘的稀释可能会降低图像质量并降低治疗效果。rhTSH 在分化型甲状腺癌的评估和 I-131 治疗中具有优势。有证据表明，这种方法可使残留放射性碘的有效半衰期延长，骨髓剂量测定改善，与激素停药相比，残留消融效果相当。然而，这需要继续服用甲状腺激素，这是一种非放射性碘的来源。将左甲状腺素转换为三碘甲状腺原氨酸以减少其非放射性碘负担值得研究，因为这可能会增强 rhTSH 的优势。
