Animal Endocrine Clinic, New York, New York, USA.
College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
J Vet Intern Med. 2021 Sep;35(5):2140-2151. doi: 10.1111/jvim.16228. Epub 2021 Aug 5.
Radioiodine ( I) is the treatment of choice for hyperthyroidism in cats, but current I-dosing protocols can induce iatrogenic hypothyroidism and expose azotemia.
To develop a cat-specific algorithm to calculate the lowest I dose to resolve hyperthyroidism, while minimizing risk of iatrogenic hypothyroidism and subsequent azotemia.
One thousand and four hundred hyperthyroid cats treated with I.
Prospective case series (before-and-after study). All cats had serum concentrations of thyroxine (T ), triiodothyronine (T ), and thyroid-stimulating hormone (TSH) measured (off methimazole ≥1 week). Using thyroid scintigraphy, each cat's thyroid volume and percent uptake of Tc-pertechnatate (TcTU) were determined. An initial I dose was calculated by averaging dose scores for T /T concentrations, thyroid volume, and TcTU; 80% of that composite dose was administered. Twenty-four hours later, percent I uptake was measured, and additional I administered, as needed, to deliver an adequate radiation dose to the thyroid tumor(s). Serum concentrations of T , TSH, and creatinine were determined 6 to 12 months later.
The median calculated I dose was 1.9 mCi (range, 1.0-10.6 mCi); 1380 cats required additional I administration on day 2. Of the cats, 1047 (74.8%) became euthyroid, 57 (4.1%) became overtly hypothyroid, 240 (17.1%) became subclinically hypothyroid, and 56 (4%) remained hyperthyroid. More overtly (71.9%) and subclinically (39.6%) hypothyroid cats developed azotemia than euthyroid cats (14.2%; P < .0001).
Our algorithm for calculating individual I doses resulted in cure rates similar to historical treatment rates, despite much lower I doses. This algorithm appears to lower prevalence of both I-induced overt hypothyroidism and azotemia.
放射性碘（I）是治疗猫甲状腺功能亢进的首选方法，但目前的 I 剂量方案可能会导致医源性甲状腺功能减退症和氮血症。
制定一种专门用于猫的算法，以计算出最低的 I 剂量来解决甲状腺功能亢进，同时将医源性甲状腺功能减退症和随后的氮血症的风险降到最低。
1400 只接受 I 治疗的甲状腺功能亢进的猫。
前瞻性病例系列（前后研究）。所有猫均在停服甲巯咪唑至少 1 周后测量血清甲状腺素（T4）、三碘甲状腺原氨酸（T3）和促甲状腺激素（TSH）浓度（off methimazole≥1 周）。使用甲状腺闪烁照相术，确定每只猫的甲状腺体积和 Tc-pertechnatate（TcTU）的摄取百分比。通过平均 T4/T3 浓度、甲状腺体积和 TcTU 的剂量评分来计算初始 I 剂量；给予该复合剂量的 80%。24 小时后，测量 I 的摄取百分比，并根据需要给予额外的 I，以向甲状腺肿瘤提供足够的辐射剂量。6 至 12 个月后，测量血清 T4、TSH 和肌酐浓度。
中位数计算的 I 剂量为 1.9mCi（范围，1.0-10.6mCi）；1380 只猫在第 2 天需要额外的 I 治疗。在这些猫中，1047 只（74.8%）变为甲状腺功能正常，57 只（4.1%）变为明显甲状腺功能减退，240 只（17.1%）变为亚临床甲状腺功能减退，56 只（4%）仍然甲状腺功能亢进。与甲状腺功能正常的猫相比，明显（71.9%）和亚临床（39.6%）甲状腺功能减退的猫更易发生氮血症（P<.0001）。
我们计算个体 I 剂量的算法导致了与历史治疗率相似的治愈率，尽管 I 剂量要低得多。这种算法似乎降低了 I 诱导的明显甲状腺功能减退症和氮血症的发生率。
