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Congenital Dyshormonogenic Hypothyroidism with Goiter (Discovered in the Shih Tzu)

Congenital Dyshormonogenic Hypothyroidism (CDH) is a rare condition causing a defect in iodide transport and a subsequent reduction in the synthesis of thyroid hormones, resulting in hypothyroidism and goiter.

Found in

1 in 5,000 dogs

in our testing

Key Signs

Hypothyroidism, Goiter, Delayed growth, Dilated cardiomyopathy

Age of Onset

At birth

Present at birth


Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with CDH

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about CDH

Clinical signs of this disorder include moderate growth delay, and goiter (swelling and enlargement of the thyroid gland). Dilated cardiomyopathy was observed in the two family members affected with this condition that were described in the case study and mutation-defining publication.

For many forms of congenital hypothyroidism, thyroid hormone replacement therapy has resulted in a successful outcome, particularly when started early in life. Due to the rarity of this form of congenital dyshormonogenic hypothyroidism in the Shih Tzu, it is unknown to what extent thyroid hormone replacement will be of benefit, however hormone replacement therapy may be a viable option for treatment.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the CDH mutation can be safely bred with a clear dog with no copies of the CDH mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the CDH mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the CDH mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene SLC5A5
Variant G>A
Chromosome 20
Coordinate 45,024,672

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Soler Arias, E. A., Castillo, V. A., Garcia, J. D., & Fyfe, J. C. (2018). Congenital dyshormonogenic hypothyroidism with goiter caused by a sodium/iodide symporter (SLC5A5) mutation in a family of Shih-Tzu dogs. Domestic Animal Endocrinology, 65, 1–8. View the article