I have
a confession to make, actually two.
First
off, I am way behind on addressing letters. Second, I
do not necessarily respond in order received. I try,
but if there is a letter describing a situation that
is more critical, I will move it to the top of the
pile.
Today's
patient would represent one of these situations.
Scud is
a 2-year-old male bearded dragon, a species of lizard
found wild in Australia. These guys are popular for
those seeking a hardy, friendly pet.
Scud,
however, is having a problem. He is shaking when he
moves, said Dana. She said the shaking seems to be
getting worse. Initially, it was quite subtle, but
lately, Scud seems to shake with every motion. His
ability to get around has decreased, but Dana says he
is eating his crickets and occasionally various green
leafed vegetables.
There
are multiple possible causes for Scud's shaking, but a
likely one is nutritional secondary
hyperparathyroidism. Now that's a mouthful.
Nutritional
secondary hyperparathyroidism is a disease that occurs
as a result of a poor calcium balance in the diet.
More correctly, it is an issue with the
calcium-to-phosphorous ratio. This disease can occur
in virtually all vertebrate animals, including humans.
If left unaddressed, it results in death.
The
pathophysiology of this disease - its mechanism of
action, if you will - involves the interaction between
the calcium taken in through diet and the parathyroid
gland, which is primarily responsible for calcium
balance in the body. Parathyroid hormone is secreted
by this gland in response to lowering calcium levels
in the blood. The response within the body is to
absorb more calcium from the gastrointestinal tract,
i.e. the food eaten. In cases of longer-term
low-calcium levels in the blood, usually because of
improper diet, calcium is robbed from the bone. It is
this cascade of events that is likely responsible for
Scud's tremors.
Calcium
is necessary for normal muscle function, but in Scud's
case, the blood level of calcium is too low and his
muscles are not able to function properly, thus
leading to the symptom of tremors.
These
lizards usually start with tiny little tremors within
muscles and then progress to uncoordinated limb and
body motion. In severe cases, these animals cannot
effectively move or even raise their bodies.
There
are cases when the tremors can come on very acutely if
the calcium level drops rapidly before the parathyroid
response can occur. This is more common in older
lizards.
What is
happening to Scud is that his calcium intake has been
too low for a while, leading to the body's response
discussed above. Because of the calcium release from
his bones, his skeleton is actually dissolving. This
is a survival mechanism, primarily because the body
cannot function without calcium and, at least
initially, this makes the bone expendable. In severe
cases, I have seen these patients with virtually no
bone density on radiographs. Surprisingly, although
logically, their blood calcium levels can be normal
owing to the calcium being liberated from the bone, at
least until there is no more bone to dissolve.
Scud's
calcium levels are low; otherwise, he would not be
showing the tremors.
Treatment
for this disease is multifaceted, depending on the
severity of the patient's calcium problem. If the
process is caught at an early stage, before the body
has responded by significantly cannibalizing its bone,
calcium supplementation in the diet can bring about
resolution. In patients with severe bone loss, we not
only have to supplement the calcium in the diet but we
must also attempt to reverse the bone-dissolving
mechanisms that have been activated as a result of
improper diet. This requires special injectable
medications and, depending on the severity of the
lizard's condition, it simply may not be possible to
cure.
There
are other factors that are involved in calcium
metabolism, including exposure to ultraviolet
wavelengths of light that affect calcium absorption
from the diet. However, that discussion is for another
time. Right now, Scud needs veterinary medical
attention and hopefully it is not too late for
something to be done.
___
(Jeff
Kahler is a veterinarian in Modesto. Questions can be
submitted to Your Pet in care of LifeStyles, The
Modesto Bee, P.O. Box 5256, Modesto, CA 95352.)