Page 12 - 2014 Le Mag 2nd Qtr
P. 12

W. Jean Dodds, DVM
938 Stanford Street
Santa Monica, CA 90403
(310) 828-4804;FAX (310) 453-5240;


Hypothyroidism is the most common endocrine disorder of dogs. More than 80% of cases

result from autoimmune thyroiditis, the heritable autoimmune disease that progressively
destroys the thyroid gland. But, classical clinical signs of hypothyroidism only appear once
more than 70% of the gland is destroyed. Accurate diagnosis may be difficult because thyroid

dysfunction produces a wide range of clinical signs, many of which are subtle and mimic those
of other causes.

Hyperthyroidism is a common endocrine disorder of older cats. Diagnosis can be confounded
by concurrent kidney, gastrointestinal, and liver disease, as total T4 concentration can be
suppressed into the normal reference range.

To facilitate diagnosis of thyroid disorders, veterinarians and their clients need to routinely utilize
more complete thyroid profiles; although there is a need to balance affordability with accuracy.

Basic Thyroid Diagnostics

Basal thyroid levels are not the same for dogs over the age and breed spectrum.
• Puppies have higher basal thyroid levels than adults
• Geriatrics have lower basal thyroid levels than adults

• Large / giant breeds have lower basal thyroid levels
• Sighthounds as a group have much lower basal thyroid levels

Situations that affect basal thyroid activity
• Basal levels affected by certain drugs
• Basal levels lowered by estrogen; raised by progesterone. Test during anestrus

• Thyroid levels are suppressed up to 25% by corticosteroids, sulfonamides, overdosing iodine
(kelp), and phenobarbital
• Rabies vaccination within previous 45 days can elevate TgAA by ~ 25%

Testing Overview


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