Thyroid and renal function in cats following low‐dose radioiodine (111Mbq) therapy by Natalie Finch and colleagues at the University of Bristol

Low‐dose radioiodine is an effective treatment for hyperthyroidism in most cats but overt hypothyroidism may develop in some. Total thyroxine and thyroid stimulating hormone monitoring should be performed post-therapy, and glomerular filtration rates (GFR) should be measured in non‐azotaemic cats to detect early declines in renal function.

Radioactive iodine (RAI) treatment is widely considered the gold standard treatment for hyperthyroidism, which is the most commonly diagnosed endocrinopathy in cats. This study assessed the effect of low‐dose (111MBq) radioiodine therapy on thyroid and renal function in hyperthyroid cats over a 12‐month follow‐up period.

After RAI treatment, two of 24 cats showed persistent hyperthyroidism, and six developed overt hypothyroidism (25%). Of these six, three (50%) developed decreased renal function, with decreased GFR preceding azotaemia in two of these three individuals. Fifteen (63%) cats achieved euthyroidism.

Thyroid function, including total thyroxine and thyroid stimulating hormone, should be monitored long‐term in all cats undergoing RAI as hypothyroidism can develop at variable rates in the first year post-treatment. In addition, renal function should ideally be monitored by GFR in non‐azotaemic cats to ensure early and accurate detection of any decline, particularly in cats with the potential to develop hypothyroidism.

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