Peer-reviewed veterinary case report
Urine concentration changes in hyperthyroid cats after radioiodine
By Peterson, Mark E & Rishniw, Mark·Published in Journal of veterinary internal medicine·2023·Animal Endocrine Clinic, United States·View original on PubMed →
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Original publication title: Urine concentrating ability in cats with hyperthyroidism: Influence of radioiodine treatment, masked azotemia, and iatrogenic hypothyroidism.
- Species:
- cat
Plain-English summary
A group of hyperthyroid cats was studied to see how their urine concentration ability changed after treatment with radioiodine. Before treatment, nearly half of the cats had low urine specific gravity (USG), which can indicate kidney issues. After treatment, most cats with normal USG continued to have good kidney function, while those with low USG were more likely to develop kidney problems. Interestingly, the treatment for hypothyroidism did not change their urine concentration ability. This suggests that if a hyperthyroid cat has low USG, it may be at a higher risk for kidney disease after treatment.
People also search for: cat hyperthyroidism treatment · cat urine specific gravity low · cat kidney disease symptoms · radioiodine treatment for cats · cat hypothyroidism effects
Abstract
BACKGROUND: Hyperthyroid cats often have urine specific gravity (USG) values <1.035. It remains unclear how USG changes after treatment, if USG can be used to predict azotemia after treatment, or how iatrogenic hypothyroidism influences USG values. OBJECTIVES: To determine the proportion of hyperthyroid cats with USG <1.035 vs ≥1.035; if USG changes after treatment; and whether USG <1.035 correlated with unmasking of azotemia or hypothyroidism. ANIMALS: Six hundred fifty-five hyperthyroid cats treated with radioiodine; 190 clinically normal cats. METHODS: Prospective, before-and-after study. Hyperthyroid cats had serum thyroxine, thyroid-stimulating hormone, and creatinine concentrations, and USG measured before and 6 months after successful treatment with radioiodine. RESULTS: Of untreated hyperthyroid cats, USG was ≥1.035 in 346 (52.8%) and <1.035 in 309 (47.2%). After treatment, 279/346 (80.6%) maintained USG ≥1.035, whereas 67/346 (19.4%) became <1.035; 272/309 (88%) maintained USG <1.035, whereas 37/309 (12%) became ≥1.035. Only 22/346 (6.4%) with USG ≥1.035 developed azotemia after treatment, compared with 136/309 (44%) with <1.035 (P < .001). Of cats remaining nonazotemic, 38% had USG <1.035, compared with 20% of normal cats (P < .001). The 137 cats with iatrogenic hypothyroidism had lower USG after treatment than did 508 euthyroid cats (1.024 vs 1.035), but USGs did not change after levothyroxine supplementation. USG <1.035 had high sensitivity (86.1%) but moderate specificity (65.2%) in predicting azotemia after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperthyroidism appears not to affect USG in cats. However, cats with evidence of sub-optimal concentrating ability before radioiodine treatment (USG < 1.035) are more likely to develop azotemia and unmask previously occult chronic kidney disease. Iatrogenic hypothyroidism itself did not appear to affect USG values.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/37668163/