The thyroid glands produce thyroid hormones, which regulate
the metabolism. Hyperthyroidism is a condition of overproduction of
thyroid hormones and increased metabolism. All the body processes
are accelerated and the body burns energy fast. The disease is
common especially in older cats and it is possible that diet and
environmental factors are responsible for the high incidence.
Common sign is progressive weight loss (despite ravenous
appetite and increased intake of food), increased water consumption
and urination and possibly periodic vomiting or diarrhea. Cats may
be hyperactive or hypoactive and display behavioral alterations.
The thyroid hormones regulate many organs and systems, such
as the heart, the liver, the digestive and nervous system. Affected
cats often develop heart problems and high blood pressure. If left
untreated the disease progresses and the cat may die of emaciation
or heart failure.
A blood test will show a high level of one of the thyroid
hormones, as well as indication of organ malfunction. Other helpful
tests are urine analysis, x-rays, EKG, blood pressure determination,
There are three choices for treatment:
1. Radioactive iodine is injected and destroys all abnormal
thyroid tissue. Treatment requires one or two weeks of
hospitalization at a veterinary hospital licensed to administer
radiation therapy. Sometimes, but not always, the expense can be
greater than for the other options.
2. Surgical removal of the affected thyroid portion is
effective. There is however a degree of risk involved. The cat is
generally hospitalized for one night following surgery. The expense
may be in the range of radiation treatment.
3. Oral medication such as Methimazole, are commonly used.
A small number of cats may develop reactions or side-effects
(vomiting, lethargy, anorexia, fever, and anemia). The drug must be
given for the remainder of the cat's life. Periodic blood tests must
be done to keep the dosage regulated. This type of treatment is
appropriate for the cat that is a poor surgical risk due to other
health problems or is exceptionally old.
The prognosis is fairly good for cats undergoing
treatment. They regain weight and normalize their metabolism and
organ function and enjoy longer quality lives.