Objective—To establish a sensitive test for the detection of autoantibodies against thyroid peroxidase (TPO) in canine serum samples.
Sample Population—365 serum samples from dogs with hypothyroidism as determined on the basis of serum concentrations of total and free triiodothyronine (T3), total and free thyroxine (T4), and thyroidstimulating hormone, of which 195 (53%) had positive results for at least 1 of 3 thyroid autoantibodies (against thyroglobulin [Tg], T4, or T3) and serum samples from 28 healthy dogs (control samples).
Procedure—TPO was purified from canine thyroid glands by extraction with detergents, ultracentrifugation, and precipitation with ammonium sulfate. Screening for anti-TPO autoantibodies in canine sera was performed by use of an immunoblot assay. Thyroid extract containing TPO was separated electrophoretically, blotted, and probed with canine sera. Alkaline phosphatase–conjugated rabbit anti-dog IgG was used for detection of bound antibodies.
Results—TPO bands were observed at 110, 100, and 40 kd. Anti-TPO autoantibodies against the 40-kd fragment were detected in 33 (17%) sera of dogs with positive results for anti-Tg, anti-T4, or anti-T3 autoantibodies but not in sera of hypothyroid dogs without these autoantibodies or in sera of healthy dogs.
Conclusions and Clinical Relevance—The immunoblot assay was a sensitive and specific method for the detection of autoantibodies because it also provided information about the antigen. Anti-TPO autoantibodies were clearly detected in a fraction of hypothyroid dogs. The value of anti-TPO autoantibodies for use in early diagnosis of animals with thyroid gland diseases should be evaluated in additional studies.
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)
Objective—To assess associations between epidemiologic
and laboratory variables and calciotropic
hormones in cats with odontoclastic resorptive
Animals—182 client-owned cats older than 1 year of
age with oral disease.
Procedure—Information on medical history, behavior,
living environment, and feeding management was
assessed by use of a questionnaire. After induction of
general anesthesia, oral examination was performed
following standardized protocols and included dental
probing and full-mouth radiography. Laboratory analyses
included evaluation of FeLV-FIV status, serum biochemical
analyses, CBC, urinalysis, and serum concentrations
of intact parathyroid hormone (iPTH),
parathyroid hormone-related peptide (PTHrP), 25-hydroxyvitamin D (25-OHD), free thyroxine (fT4), and
ionized calcium (iCa).
Results—ORLs were identified in 72.5% of cats.
Mandibular third premolars were the most commonly
affected teeth. Cats with ORLs were significantly
older (mean, 9.2 years) than cats without ORLs
(mean, 6.6 years). Multivariate logistic regression
analysis revealed that 25-OHD, urine specific gravity,
jaw-opening reflex on probing, and missing teeth
were significant variables, even after accounting for
age. Cats with ORLs had significantly higher mean
serum concentration of 25-OHD (112.4 nmol/L) and
significantly lower mean urine specific gravity
(1.0263), compared with cats without ORLs (89.8
nmol/L and 1.0366, respectively).
Conclusions and Clinical Relevance—Results did
not indicate associations between iPTH, PTHrP, or fT4
and development of ORLs. In affected cats, the
importance of high serum 25-OHD and low urine specific
gravity has not been determined. (Am J Vet Res 2005;66:1446–1452)
Objective—To assess use of serum thyroid hormone concentrations by veterinarians to diagnose hypothyroidism in sighthounds and to evaluate serum thyroid hormone concentrations in healthy Salukis.
Design—Retrospective case series and cross-sectional study.
Animals—398 sighthounds of various breeds with a diagnosis of hypothyroidism and 283 healthy Salukis.
Procedures—Pretreatment thyroid hormone assay results from sighthounds subsequently classified as hypothyroid by practitioners were retrieved from a laboratory database. In healthy Salukis, serum concentrations of total thyroxine (T4), free T4, total triiodothyronine (T3), free T3, and thyroid-stimulating hormone (TSH) and antibodies against thyroglobulin and thyroid hormones were assayed.
Results—Records indicated hypothyroidism had been diagnosed in 303 (76.1%) sight-hounds on the basis of low serum thyroid hormone concentrations alone and in 30 (7.5%) others despite all thyroid hormone indices being within reference limits. Only 65 (16.3%) dogs had a high TSH concentration or positive thyroglobulin autoantibody result to support the diagnosis. In healthy Salukis, median (reference limits) serum concentrations of total T4, free T4, total T3, free T3, and TSH were 13.0 nmol/L (2.8 to 40.0 nmol/L), 12.0 pmol/L (2.0 to 30.3 pmol/L), 1.0 nmol/L (0.4 to 2.1 nmol/L), 4.0 pmol/L (1.6 to 7.7 pmol/L), and 0.18 ng/mL (0 to 0.86 ng/mL), respectively.
Conclusions and Clinical Relevance—Diagnosis of hypothyroidism by practitioners was most often made without adequate supportive laboratory evidence. Thyroid hormone values in healthy Salukis differed markedly from standard reference limits for some, but not all, thyroid hormone indices. Breed-specific reference limits should be used when interpreting thyroid hormone profiles of sighthounds.
Objectives—To determine the effects of racing and
training on serum thyroxine (T4), triiodothyronine (T3),
and thyroid stimulating hormone (TSH) concentrations
Animals—9 adult racing Greyhounds.
Procedure—Serum thyroid hormone concentrations
were measured before and 5 minutes after a race in
dogs trained to race 500m twice weekly for 6 months.
Resting concentrations were measured again when
these dogs had been neutered and had not raced for
3 months. Postrace concentrations were adjusted relative
to albumin concentration to allow for effects of
hemoconcentration. Thyroid hormone concentrations
were then compared with those of clinically normal
dogs of non-Greyhound breeds.
Results—When adjusted for hemoconcentration,
total T4 concentrations increased significantly after
racing and TSH concentrations decreased; however,
there was no evidence of a change in free T4 or total
or free T3 concentrations. Resting total T4 concentrations
increased significantly when dogs had been
neutered and were not in training. There was no evidence
that training and neutering affected resting
TSH, total or free T3, or free T4 concentrations.
Resting concentrations of T3, TSH, and autoantibodies
against T4, T3, and thyroglobulin were similar to those
found in other breeds; however, resting free and total
T4 concentrations were lower than those found in
Conclusions and Clinical Relevance—Except for
total T4, thyroid hormone concentrations in
Greyhounds are affected little by sprint racing and
training. Greyhounds with low resting total and free T4
concentrations may not be hypothyroid. (Am J Vet