The two primary thyroid problems in cats are hyperthyroidism and hypothyroidism. In hyperthyroidism, a cat's body produces too much of the thyroid hormone; in hypothyroidism, it produces too little. Of the two, hyperthyroidism is more common, but hypothyroidism can become an issue for cats after they have been treated for hyperthyroidism. For this reason, it's crucial for pet owners to closely monitor their cats after hyperthyroidism treatment.
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Appetite and Weight
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A hyperthyroid cat has a higher rate of metabolism. Often, the faster metabolism leads to an increase in appetite as well as significant weight loss. The cat with hypothyroidism often eats less. Her slower metabolic rate makes her vulnerable to weight gain to the point of obesity, despite her decreased appetite.
Thirst, Vomiting and Litter Box Use
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Increased thirst and water intake is a classic sign of hyperthyroidism, resulting in more trips to the litter box. In addition to frequent urination, it's normal for a hyperthyroid cat to vomit and experience diarrhea and loose stool. The hypothyroid cat is prone to constipation.
Physical Changes
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Thyroid condition can't be determined merely by looking at a cat's coat because both thyroid problems affect her coat's condition. Her coat may be dull and/or thinning and her skin flaky and dry. Hair loss is also normal. A hyperthyroid cat may experience rapid nail growth and have thick, fragile nails. She may also have a rapid heart rate, labored breathing, tremors and weakness. A hypothyroid cat tends to have a lower body temperature, prompting her to seek warmer places to spend her time.
Behavior
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An increased energy level is common for a cat with an overactive thyroid. As well, a hyperthyroid cat will appear restless and nervous, and often engage in pacing and night yowling, emitting long, mournful cries during the night hours. A hypothyroid cat doesn't exhibit such anxiety; instead, she tends to be lethargic and spends more time than normal sleeping. About five percent of hyperthyroid cats exhibit apathetic hyperthyroidism, where they appear depressed, weak or apathetic along with weight loss and a depressed appetite.
Diagnosis
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Hypothyroidism is quite rare in cats and usually occurs from treatment of hyperthyroidism. Diagnosing a thyroid hormone disorder involves a thorough medical exam by the vet, who may feel the enlarged gland during a physical exam. The vet will consider the cat's medical history and symptoms, as well as perform blood tests to measure thyroid hormone levels. A thyroid scan can also help confirm hyperthyroidism.
Treatment
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There are several options for treating hyperthyroidism. Radioiodine therapy is the preferred method of treatment among veterinarians, as it offers a safe, permanent cure to the condition. Prescription medication known as methimazole is effective in controlling thyroid hormone levels, however, it's a life-long commitment and usually requires two daily doses. As well, the cat must have her thyroid function monitored regularly by the vet to ensure her hormone levels are correct. Surgery is a less popular option, as it can be difficult for the vet to remove the correct amount of tissue and older cats may have problems coping with anesthesia. Occasionally, treating hyperthyroidism can result in an overly sluggish thyroid. If the cat becomes hypothyroid, the vet will prescribe a thyroid hormone supplement to bring the cat's hormone levels into balance.
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