Did You Know?
Feline Hyperthyroidism/Canine
Hypothyroidism
Feline Hyperthyroidism
The thyroid gland plays a very important role in regulating the
body’s rate of metabolism. Hyperthyroidism is a disorder
characterized by the excess production of thyroid hormone and a
subsequent increase in the metabolic rate. This is a fairly
common disease of older cats. The thyroid glands usually enlarge
in this disease but this is a non-malignant change (benign.)
Less than 2% of hyperthyroid cases involve a malignancy.
Contributing Factors
Advancing age is the main factor that increases a cat’s risk for
hyperthyroidism. Environmental and dietary risk factors have
been investigated and at this time there is no correlation
between these items and hyperthyroid disease.
No individual breed is known to be at increased risk, although
the Siamese Cats appear to have a 10-fold lower risk of
developing hyperthyroidism than other breeds.
Clinical Signs
The typical cat with hyperthyroidism is between 7-15 years of
age. The most consistent finding with this disorder is weight
loss secondary to an increased rate of metabolism. The cat
attempts to compensate for this by increasing their appetite. In
fact, some of these cats have a ravenous appetite and will
literally eat anything in sight! Despite the increased intake of
food, most cats gradually lose weight. The weight loss may be so
gradual that some owners won’t even realize it has occurred.
There may be periodic diarrhea, and the hair coat may look poor
or unkempt. In some cats, anorexia develops as the disease
progresses further.
Two secondary complications as a result of Hyperthyroidism can
be significant. These include hypertension (high blood pressure)
and Heart disease called hypertrophic cardiomyopathy.
Hypertension develops as a consequence of the increased pumping
of the heart. In some cats, blood pressure can become so high
that retinal hemorrhage or detachment will occur and result in
sudden blindness. Both of these problems are reversible, to a
degree, with appropriate and timely treatment of the disease.
If you feel your cat may suffer from any of the above signs,
please give us a call to set up an appointment to see a doctor
at LLAMC.
Canine Hypothyroidism
The thyroid gland is one of the most important glands in the
body. It is located in the neck near the trachea and is composed
of two lobes, one on each side of the trachea (windpipe). The
gland is controlled by the body’s master gland, the pituitary
gland, located at the base of the brain.
The thyroid gland regulates the rate of metabolism. If it is
hyperfunctional, metabolism speeds up. If it is less functional
than normal, metabolism slows down. The latter is the basis for
the clinical signs of hypothyroidism.
Causes
Hypothyroidism is almost always caused by one of two diseases:
lymphocytic thyroiditis or idiopathic thyroid gland atrophy. The
former disease is the most common cause of hypothyroidism and is
thought to be an immune-meditated disease. This means that the
immune system decides that the thyroid is abnormal or foreign
and tries to destroy it. It is not known why the immune system
does this. These two causes of hypothyroidism account for more
than 95% of the cases. The other five percent are due to
uncommon diseases, including cancer of the thyroid gland.
Clinical Signs
When the rate of metabolism slows down, virtually every organ in
the body is affected in some manner. Most affected dogs have one
several “typical” physical and/or chemical abnormalities. These
include:
-
Weight gain without an increase in appetite
-
Lethargy and lack of desire to exercise
-
Cold intolerance (gets cold easily)
-
Dry hair coat with excessive shedding
-
Very thin hair coat to near baldness
-
Increased pigmentation in the skin
-
Increased susceptibility to skin and ear infections
-
Failure to regrow hair after clipping or shaving
-
High blood cholesterol
Some dogs also have other abnormalities that are not the typical
findings. Which include:
-
Thickening of the facial skin so they have a “tragic facial expression”
-
Abnormal function of nerves causing non-painful lameness, dragging of feet and a head tilt
-
Loss of libido and infertility in intact males
-
Lack of menstrual cycling, infertility, and abortion in females
-
Fat deposits in the corneas of the eyes
-
Keratoconjuntivitis Sicca (“dry eye” due to lack of tears)