Urine concentrating ability in cats with hyperthyroidism: Influence of radioiodine treatment, masked azotemia, and iatrogenic hypothyroidism.

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.