Coral Springs Animal Hospital's Pawfessional Spring 2017 | Page 11
Although rare, iodine deficiency
has been reported to cause
hypothyroidism in kittens fed a
strict all-meat diet.
The clinical signs of congenital
hypothyroidism are similar to those
in dogs. Affected kittens typically
appear normal at birth, but a
decrease in growth rate usually
becomes evident by 6-8 weeks of
age. Disproportionate dwarfism
develops over the ensuing months,
with affected kittens developing
large heads, short broad necks and
short limbs. Additional findings
include lethargy, mental dullness,
constipation,
hypothermia,
bradycardia
and
prolonged
retention of deciduous teeth. The
hair coat may consist mainly of
undercoat with primary guard hair
scattered thinly throughout.
Unlike the dog, the demand for
accurate tests to assess thyroid
gland function in the cat has been
driven by the need to distinguish
normal from hyperthyroid cats, not
from those that might be
hypothyroid.
Measurement
of
baseline T4 and FT4 concentrations
by equilibrium dialysis have been
effective in diagnosing feline
hyperthyroidism. Currently, there is
no feline-specific TSH assay. Many
of the tests used to asses thyroid
gland function in the dog have not
been
critically
evaluated
or
developed in the cat. In most
situations, assessment of thyroid
gland
function
relies
on
measurement of baseline serum T4
and FT4 concentrations (reference
range for T4 and FT4 1-4 ng/dL).
Treatment of hypothyroidism is
similar for the cat and dog.
Levothyroxine is the recommended
thyroid hormone supplement. The
initial dosage for cats is 0.05 mg or
0.1 mg orally once daily. A minimum