Open AccessEfficacy of Low‐dose (2 millicurie) versus Standard‐dose (4 millicurie) Radioiodine Treatment for Cats with Mild‐to‐Moderate Hyperthyroidism
Author(s) -
Lucy J.M.,
Peterson M.E.,
Randolph J.F.,
Scrivani P.V.,
Rishniw M.,
Davig D.L.,
Thompson M.S.,
Scarlett J.M.
Publication year - 2017
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.14646
Subject(s) - medicine , azotemia , subclinical infection , cats , creatinine , gastroenterology , prospective cohort study , endocrinology , renal function , urology
Background Radioiodine ( 131 I) is effective treatment for hyperthyroidism in cats, but optimal dose to restore euthyroidism without inducing hypothyroidism is unclear. Treatment‐induced hypothyroidism can lead to azotemia and reduced duration of survival. Objective To compare efficacy and short‐term outcomes of low‐dose 131 I versus higher, standard‐dose 131 I as treatment for hyperthyroidism. Animals A total of 189 client‐owned cats undergoing 131 I treatment for mild‐to‐moderate hyperthyroidism (serum T 4 ≥ 4.0 μg/ dL and <13.0 μg/ dL ). Methods Prospective, nonrandomized, cohort study comparing treatment with either low‐dose (2 mC i, n = 150) or standard‐dose (4 mC i, n = 39) 131 I. Serum T 4 , thyroid‐stimulating hormone ( TSH ), and creatinine concentrations were measured after 1, 3, and 6 months to determine persistent hyperthyroidism, overt hypothyroidism (low T 4 , high TSH ), subclinical hypothyroidism (normal T 4 , high TSH ), and azotemia. Results There was no significant difference in prevalence of cats with persistent hyperthyroidism between standard‐ and low‐dose treatment groups at 3 (0% versus 5.3%; P = .34) and 6 (0% versus 3.3%; P = .51) months. Overt (18% versus 1%; P = .0005) or subclinical (46% versus 21%; P = .004) hypothyroidism was more common in cats at 6 months after standard‐dose 131 I. No difference in incidence of azotemia existed between groups, but cats treated with standard‐dose 131 I had higher creatinine concentrations ( P < .05) and higher percent rises in creatinine ( P < .0001). Conclusions and Clinical Importance Low‐dose 131 I is safe and effective for cats with mild‐to‐moderate hyperthyroidism, as evidenced by a cure rate of >95% with reduced frequency of iatrogenic hypothyroidism and azotemia.