Important information for veterinarians

Examination prior to admission to medical care

2-3 weeks old

Blood: biochemistry and hematology (geriatric profile including SDMA)
Urine: density, dipstick, sediment, UP:UC ratio, urine culture (uricult). Urine must be collected by cystocentesis.
Description of abdominal sonography
If there is a palpable nodule on the neck, consultation is necessary, as surgical treatment may be appropriate first.

Requirements on the day of arrival

Without thyrostatic drugs (Apelka®, etc.) since Wednesday of the previous week
Hyperthyroidism must be confirmed and the kidneys examined.
Cats with kidney failure are not suitable candidates
Hill’s y/d diet: discontinue 3 weeks prior to therapy

Course of treatment and hospitalization

EXAMINATION ON THE DAY OF ARRIVAL

Control blood sampling for tT4, TSH, SDMA
Thyroid Scintigraphy

HOSPITALIZATION

I131 radioiodine therapy is administered as a single intravenous injection, with the dose determined on the basis of previous examinations.
Hospitalization until Friday (4–5 days).

HOME CARE AFTER THERAPY

Collect excrement for 14 days, then keep it outside your home for another 14 days.
Limit physical contact, maintain a distance of approx. 1-2 m.
Children without any interaction for 14 days.
Pregnant women without physical contact for 14 days.

Follow-up care

After the procedure

If the response to treatment is correct, the patient’s condition will gradually improve during the first 1-3 months. In 85% of patients, thyroid hormone levels will normalize within a month, and in 95% of patients within 3 months. If thyroid hormone levels remain high after 4 months, the cat may need to repeat radioactive iodine therapy. Immediately after radioiodine therapy, cats usually do not need any further treatment.

Transient hypothyroidism may occur, causing a slight decrease in tT4 levels below the minimum reference range of the laboratory where the blood is tested. This condition is not pathological/life-threatening if it does not last longer than 4-6 months.

The cat’s blood will need to be checked 1, 3, and 6 months after therapy—we are mainly interested in kidney parameters (SDMA, creatinine), tT4, and TSH. Kidney parameters are important for the early detection of masked CKD, and tT4 and TSH together can detect hypothyroidism caused by an excessively high dose of radioiodine, which can happen even with accurate dose calculation. It is very important to detect hypothyroidism and start treating it in time, before it causes kidney damage and the subsequent development of CKD.

In cats with CKD Iris stage 1-2, tT4 and TSH should be checked 14 days after radioiodine administration, as untreated hypothyroidism could lead to a significant reduction in glomerular filtration and, as a result, the development of renal failure. Therefore, levothyroxine supplementation should be started early in these cats.

If a cat shows typical clinical signs of hyperthyroidism (weight loss, diarrhea, vomiting), urgent tT4 testing is necessary.

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