Feline hypothyroidism is an uncommon endocrine disorder that requires a comprehensive history and testing to diagnose.
Typically, this condition is iatrogenic – caused by radioactive iodine (131I) or anti-thyroid medication – but can also be congenital in cats.
Contents
Diagnosis
Hypothyroidism is a disorder in which your cat’s thyroid gland fails to produce enough of the hormones necessary for normal body functioning. Signs of this deficiency may include lethargy, mental dullness, hair loss, low body temperature and decreased appetite.
Your veterinarian will conduct a complete physical exam to check for any common signs of hypothyroidism in your cat. They may also administer a blood test to measure thyroid hormone levels and make any necessary recommendations.
Hypothyroidism should be confirmed with a total thyroid function (T4) test, which typically shows a T4 concentration between 1.5 ug/dL and 2.0 ng/mL combined. A high serum TSH concentration (>1.0 ng/mL) also confirms this diagnosis and necessitates treatment.
Medications
Hypothyroidism in cats is typically treated with synthetic thyroid hormone replacement drugs like levothyroxine. These medications help regulate your cat’s thyroid levels and alleviate symptoms, but must be given for the rest of their life.
Other treatments for hyperthyroidism include medical management, surgery to remove abnormal thyroid tissue and radioactive iodine treatment. Depending on the cause of your cat’s hyperthyroidism, the medication used will vary.
Methimazole is an antithyroid drug that will prevent your cat’s thyroid hormone production. Unfortunately, it doesn’t cure the problem or kill tumor cells, so treatment must continue for life. Methimazole may have side effects like vomiting, weight loss and anorexia which must be used with care.
Monitoring
The butterfly-shaped thyroid gland in your cat’s neck is responsible for controlling their metabolism and growth. If their thyroid does not produce enough thyroid hormones, this condition is known as hypothyroidism.
Hypothyroidism can be caused by an iodine deficiency, cancer, or congenital disease (thyroid gland abnormalities). In most cases, oral medications are prescribed to treat this condition.
Tests to diagnose hypothyroidism in cats include serum FT4 concentration, which measures the non-protein bound form of thyroxine.
Another test to check for thyroid disease in cats is serum total T4. This common screening test should be done if your veterinarian suspects your cat might have thyroid disease, especially if they have displayed any symptoms or a palpable thyroid nodule during physical examination.
Prevention
The butterfly-shaped thyroid gland in your cat’s neck produces two hormones, T3 (triiodothyronine) and T4 (thyroxine), that regulate many functions such as food metabolism, growth, heart function, mental/muscle development and immunity.
Hypothyroidism in cats occurs when their thyroid gland produces insufficient amounts of the essential hormones T3 and T4, leading to an imbalance across all bodily organs.
Cats may experience a variety of symptoms, but some of the more common signs include dwarfing, extreme lethargy, mental dullness, constipation and loss of appetite. In some instances, you may even observe an altered heart rate.
Hypothyroidism in cats is treated with medications to supplement low levels of thyroxine. These are usually synthetic hormones given to your cat on a regular basis.
