Veterinarian Column: Hyperthyroidism in Cats

In the previous column, I explained about hypothyroidism in dogs, but cats often develop hyperthyroidism rather than hypothyroidism. This disease often develops in older cats, and due to excessive secretion of thyroid hormones, various symptoms are observed, including weight loss, increased activity, and excessive drinking and urination. In this article, we will explain in detail about hyperthyroidism in cats.

cause

・Nodular hyperplasia of the thyroid gland

・Adenoma

・Adenocarcinoma

symptoms

·Weight loss

・Changes in behavior (hyperactivity, increased aggression)

- Polydipsia and polyuria

・Gastrointestinal symptoms (loss of appetite, vomiting, diarrhea, polyphagia)

・Rough and stiff coat

・Tachycardia

・High blood pressure

・Abnormalities in blood tests (slightly elevated ALT and ALP )

diagnosis

Thyroid hormone will be measured.

Hyperthyroidism is diagnosed when the thyroid hormone T₄ (thyroxine) is high. Even if the test result is normal, if there are any suspicious symptoms, T₄ should be measured again at a later date, or a judgment should be made in combination with fT₄ (free thyroxine).

treatment

・Medical therapy: administration of antithyroid drugs

After starting antithyroid drug administration, tests such as T₄ measurement, blood tests (kidney function, etc.), and blood pressure measurements are required at intervals of about 2 weeks until the blood concentration stabilizes.

*Cats with hyperthyroidism are often elderly and may have chronic renal failure . Chronic renal failure may become latent due to increased renal blood flow due to excess thyroid hormone. Therefore, latent chronic renal failure may become noticeable after administration of antithyroid drugs. After starting treatment, blood tests must be performed regularly to monitor kidney function and side effects.

・Surgical therapy: Thyroidectomy

If it is difficult to continue taking oral medication, or if the patient is relatively young and a thyroid mass is evident, removal of the affected side of the thyroid may be selected.

-Dietary therapy: Feed only a low iodine diet (Hills y/d ).

A low-iodine diet suppresses the production and release of excess thyroid hormone. However, if you give them even a small amount of other food, it becomes meaningless. Even with dietary therapy, regular T₄ measurements, blood tests (kidney function, etc.), and blood pressure measurements are required.

Hyperthyroidism is a disease commonly seen in older cats. If you notice symptoms such as weight loss, loss of appetite, or diarrhea, don't blame it on age; take your pet to a veterinarian. In order for your pet to live a long and healthy life, we recommend regular health checkups.