Objective—To determine prevalence of thyroid hormone
autoantibodies (THAA) in serum of dogs with
clinical signs of hypothyroidism.
Sample Population—287,948 serum samples from
dogs with clinical signs consistent with hypothyroidism.
Procedure—Serum THAA were detected by use of a
radiometric assay. Correlation and X2 analyses were
used to determine whether prevalence varied with
breed, age, sex, or body weight. Only breeds for
which ≥ 50 samples had been submitted were used
for analysis of breed prevalence.
Results—Thyroid hormone autoantibodies were
detected in 18,135 (6.3%) samples. The 10 breeds
with the highest prevalence of THAA were the
Pointer, English Setter, English Pointer, Skye Terrier,
German Wirehaired Pointer, Old English Sheepdog,
Boxer, Maltese, Kuvasz, and Petit Basset Griffon
Vendeen. Prevalence was significantly correlated
with body weight and was highest in dogs between 2
and 4 years old. Females were significantly more likely
to have THAA than were males.
Conclusions and Clinical Relevance—Thyroid hormone
autoantibodies may falsely increase measured
triiodothyronine (T3) and thyroxine (T4) concentrations
in dogs; results suggest that T3 concentration may be
falsely increased in approximately 57 of 1,000 dogs
with hypothyroidism and that T4 concentration may
be falsely increased in approximately 17 of 1,000
dogs with hypothyroidism. Results also suggested
that dogs of certain breeds were significantly more or
less likely to have THAA than were dogs in general.
(J Am Vet Med Assoc 2002;220:466–471)