Thyroid scintigraphy is a key tool for diagnosing and staging hyperthyroidism in cats, but follow-up scintigraphic studies after radioiodine treatment are limited. This multicentric study evaluated ^99mTc-pertechnetate scintigraphy findings in 234 hyperthyroid cats before and 6 months after radioiodine treatment. Based on serum T4 and TSH concentrations, 165 (70.5%) became euthyroid, 54 (23.1%) had subclinical hypothyroidism, and 15 (6.4%) developed overt hypothyroidism. On post-treatment scintigraphy, all cats showed reduced size and radionuclide uptake of "hot" thyroid nodules. Of 99 cats with unilateral nodules, 60 (61%) recovered function in the contralateral lobe. Among 135 cats with bilateral nodules, both lobes remained visible in 108 (80%). Persistent "hot" nodules with high thyroid/salivary (T/S) ratios or thyroidal pertechnetate uptake (TcTU) occurred in 26 (11%) cats, all of which were euthyroid. Conversely, 24 (10.4%) cats had minimal or absent thyroid tissue with 17 (71%) being hypothyroid, but seven (29%) were euthyroid. As a diagnostic test for iatrogenic hypothyroidism, TcTU showed the highest sensitivity (62.3), with the T/S ratio (7.3) and background-corrected T/S ratio (30.4) being much lower (p < 0.01). While follow-up scintigraphy aids in assessing thyroid tumor destruction and residual function, its diagnostic utility for differentiating euthyroidism and hypothyroidism is limited, especially for cats with mild (subclinical) hypothyroidism.

Keywords: 131I; 99mTc-pertechnetate; hyperthyroidism; hypothyroidism; radioactive iodine.

甲状腺闪烁显像术是诊断和评估猫甲状腺功能亢进症的关键工具，但在放射性碘治疗后的随访闪烁显像研究有限。这项多中心研究评估了234只在放射性碘治疗前后使用99mTc- perchlorate（99mTc- perchlorate是一种放射性同位素）进行甲状腺闪烁显像的甲状腺功能亢进猫的结果。根据血清T4和TSH浓度，165只（70.5%）猫咪恢复了正常的甲状腺功能（称为“正常甲状腺状态”），54只（23.1%）患有亚临床性甲状腺机能减退症，而15只（6.4%）发展为显性的甲状腺机能减退症。在治疗后的闪烁显像中，所有猫的“热结节”的大小和放射性碘摄取量都减少了。“热结节”指的是那些过度活跃、产生过多甲状腺激素的结节。在99只有单侧结节的猫咪中，60只（61%）对侧腺体恢复了功能；而在135只有双侧结节的猫咪中，两个腺体在治疗后仍然可见的比例为108只（80%）。26只（11%）猫在治疗后仍存在“热”结节，这些结节具有较高的甲状腺/唾液比率或99mTc摄取率，但所有这26只猫咪都恢复到了正常的甲状腺功能状态。相比之下，有24只（10.4%）猫咪的甲状腺组织减少或消失，其中71%发展为甲状腺机能减退症，而剩余的29%保持了正常的功能水平。作为诊断医源性甲状腺机能减退症的检测手段，99mTc摄取率显示出了最高的灵敏度（62.3），相比之下，甲状腺/唾液比率（7.3）和背景校正后的甲状腺/唾液比率（30.4）则显著较低（p < 0.01）。虽然随访闪烁显像有助于评估甲状腺肿瘤破坏情况及剩余功能，但在区分正常甲状腺状态与甲状腺机能减退症方面的诊断效用是有限的，尤其是对于那些有轻微（亚临床性）甲状腺机能减退症状的猫咪。