OFA
CANINE THYROID REGISTRY
RAY NACHREINER, D.V.M., Ph.D.
BACKGROUND INFORMATION
Autoinimune Thyroiditis is the most common cause of primary hypothyroidism in dogs. The disease
has variable onset, but tends to clinically manifest itself at 2 to 5 years of age. Hence, dogs may be
clinically normal for years, only to become hypothyroid at a later date. The markers for autoimmune
thyroiditis, autoantibody formation (autoantibodies to thyroglobulin, T4 or T3), usually occur prior
to the occurrence of clinical signs. The majority of dogs that develop autoantibodies have them by 3
to 4 years of age. Development of autoantibodies at any time in the dog's life is an indication that
the dog, most likely, has the genetic form of the disease. Using today's technology, only a small
fraction of false positive tests occur.
As a result of the variable onset of the presence of autoantibodies, periodic testing will be necessary.
Dogs that are negative at 1 year of age may become positive at 6 years of age. Hence, dogs should
be tested every year or two in order to be certain that they have not developed the condition. Since
the majority of affected dogs will have autoantibodies by 4 years of age, annual testing for the first 4
years is recommended. After that, testing every other year should suffice. Unfortunately, a negative
at any one time will not guarantee that the dog will not develop thyroiditis.
The registry data can be used by breeders in determining which dogs are best for their breeding
program. Knowing the status of the dog and the status of the dog's lineage, breeders and genetic
counselors can decide which matings are most appropriate for reducing the incidence of autoimmune
thyroiditis in the offspring.
GENERAL PROCEDURES
1. Purposes - To identify those dogs that are phenotypically normal for breeding programs and to
gather data on the genetic disease - autoimmune thyroiditis.
2. ExamInation and Classification - Each dog is to be examined by an attending veterinarian and
have a serum sample sent to an OFA approved laboratory for testing according to the enclosed
application and general information instructions. The laboratory fee will be determined by the
approved laboratory. Check with the referral laboratory for special sample handling and tests for
registry purposes.
3. Certification - A ceitificate and breed registry number will be issued to all dogs
found to be normal at 12 months of age. Ages will be used in the certification process
since the classification can change as the dog ages and the automimune disease
progresses. The OFA fee is $15.00 and no charge will be made for recertification at
a later age. It is recommended that reexamination occur at ages 2,3,4,6 and 8 years.
4. Preliminary evaluation - Evaluation of dogs under 12 months of age can be performed for private
use of the owner since a few dogs are already positive at that age. However, certification will not be
possible at that age.
5. Dogs with autoimmune thyroldltls - All data, whether normal or abnormal, is to be submitted for
purposes of completeness. There is no OFA fee for entering an abnormal evaluation of the thyroid
into the data bank. Information on results determined to be positive or equivocal will not be made
public without the explicit written permission of the owner or agent
6. ThyroId abnormalities fall Into several categories - Two types will be defined by the registry.
a. Autoinimune Thyroiditis
b. Idiopathically Reduced Thyroid Function
Autoimmune thyroiditis is known to be heritable.
7. Those dogs with laboratory results that are questionable - therefore, not definitive - will be
considered as ecjuivocal. it is recommended that the test be repeated in 3-6 months.
CLASSIFICATION
The method for classifying the thyroid status will be accomplished using state of the art assay
methodology.
Indices of thyroiditis:
a. Free by dialysis (FT4D) - this procedure is considered to be the "gold standard" for assessment of
the thyroid's production and cellular availability of thyroxin. FT4D concentration is expected to be
decreased in dogs with thyroid dysfimction due to autoimmune thyroiditis.
b. Canine Thyroid Stimulating Hormone (cTSH) - This procedure helps determine the site of the
lesion in cases of hypothyroidism. hi autoimmune thyroiditis, the lesion is at the level of the thyroid
and the pituitary gland functions normally. The cTSH concentration is expected to be abnormally
elevated in dogs with thyroid atrophy from autoimmune thyroiditis.
c. Thyroglobulin Autoantibodies (TgAA) - This procedure is an indication of the presence of the
autoimmune process m the dog's thyroid.
CERTIFICATION
a. Normal FT4D Within normal range cTSH Within normal range
TgAA Negative
b. Positive autoinimune thyroiditis FT4D Less than normal range cTSH Greater than normal range
TgAA Positive
c. Positive compensative automimune thyroiditis FT4D Within normal range
cTSH Greater than normal range or
Equal to normal range
TgAA Positive
d. Idiopathically reduced thyroid function FT4D Less than normal range cTSH Greater than normal
range TgAA Negative
e. All other results are considered equivocal
LABORATORY CERTIFICATION
The laboratory certification process will include quality control, quality assurance and reagent
certification.
Laboratories may apply and, if successful, will be approved to perform analyses for OFA thyroid
certification. A site visit by a qualified veterinary endocrinologist chosen by OFA will be required
and continued quality assurance and quality control will be necessary to maintain certification. Fully
certified status can be obtained by passing the site visit and passing the results of the first OFA
quality assurance assay result test.
The approved laboratory must be contacted for the appropriate submission fonns, ample handling
procedures and laboratory service fee before collectlnz the sample. Currently, samples may be
submitted to:
Animal Health Diagnostic Laboratory
Michigan State University
517-353-0621
OR.
Diagnostic Laboratory
New York State College of Veterinary Medicine
Cornell University
607-253-3673
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