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Congenital Hypothyroidism with Goiter occurs in newborn puppies, kittens, goats, and lambs.  Thanks to MSU and Dr. Fyfe it is is well studied in dogs.




CHG 3: Congenital Hypothyroidism with Goiter

John C. Fyfe, D.V.M., Ph.D.

Part 3 of 4, exclusive 2014 interview plus 2019 Update


Dr. Fyfe and MSU announce canine DNA-based carrier test for deadly Congenital Hypothyroidism with Goiter which can occur in newborn puppies.


Congenital Hypothyroidism With Goiter is a "thyroid problem" but is unlike idiopathic, dietary, or environmentally induced thyroid hormone imbalance. If you suspect puppy loss due to CHG, have your veterinarian submit samples to Dr. John Fyfe at Michigan State University (info below). If you missed important background and CHG disease information, go to Part 1 - CHG Introduction and Part 2 - About Congenital Hypothyroidism with Goiter (CHG).


Genetic Basis and Cause for CHGGG


Dr. John C. Fyfe - In a cooperative effort of breeders, veterinarians, and a canine genetics researcher at the Michigan State University College of Veterinary Medicine, the genetic basis of congenital hypothyroidism with goiter (CHG) in Toy Fox Terriers (TFT) has been discovered, and a DNA-based carrier test is now available. Thyroid hormone is essential for normal development and metabolism in dogs, especially in the rapid growth period that puppies experience. Pups affected with CHG are abnormal from just a few days of age. They do not move around as much as normal pups, and the head may appear large in comparison to the body. Most have died or were euthanized by 3 weeks of age. If nursing care is given and they survive as long as 3 weeks, the eyes do not open, the ear canals remain very small, and the hair coat is abnormally bristly. By the second week of age, a swelling on the underside of the neck can be felt and continues to enlarge with time. The swelling may be mistaken for lymph nodes in making an incorrect diagnosis of puppy strangles. Delay in lengthening of bones in the legs, spine, and face causes dwarfism. Most all abnormalities are alleviated by early diagnosis and daily oral administration of thyroid hormone medication, but this does not stop the goiter from continuing to enlarge and constricting the airway. Even treated, this is a disfiguring disorder. Many TFT breeders have been aware for years that pups as described above have been born occasionally, but until recently few have received a correct diagnosis or indication that the disorder was inherited. Affected puppies have occurred in breeding programs across the United States of America and in New Zealand.


Before you speculate, the case(s) referenced in other veterinary sources has never been confirmed. CHG has however been confirmed in other breeds and even other species including cats.


Recent studies have demonstrated that the disorder is inherited as a simple autosomal recessive trait. For a puppy to have CHG, it must received the mutated copy (allele) of the disease gene from both parents, and male and female puppies are equally affected. The parents of affected pups show no outward signs of disease, but they are obligate carriers, by definition. In a breeding program, both male and female carriers will pass on their mutant alleles to 50% of all their offspring, on average. When two carriers are inadvertently mated, on average 25% of the puppies will have CHG. That means that in litters from such matings, there may be some combination of CHG and normal pups, all CHG puppies, or all normal puppies. Unidentified carriers in breeding programs continue to spread the mutant allele throughout the TFT breed.


This test is offered to TFT breeders through the Laboratory of Comparative Medical Genetics at Michigan State University in hopes that it will be used to eliminate CHG from TFT breeding programs. Testing results are given only to the person submitting the dog’s sample and are kept strictly confidential. For instructions on submitting samples, please point your internet browser to


Contact Dr. John C. Fyfe by email or at the address below.

John C. Fyfe, D.V.M., Ph.D.

Laboratory of Comparative Medical Genetics

2209 Biomedical Physical Sciences

567 Wilson Road

Michigan State University

East Lansing, MI 48824

Phone: (517) 884-5348    About John Fyfe, DVM, PhD

We are trying to determine If any study data was released to the Toy Fox Terrier Club or to OFA.  If you KNOW of a Toy Fox Terrier litter that contained congenital hypothyroidism with goiter (CHG) we ask you to email the editor.  If you request anonymity, we will respect your wishes.  The numerical results of this new 2019 survey will be reported here and to the Toy Fox Terrier Club Of America.


If you know of a breed club that keeps CHG records, email Editor and we will contact them. EST 1998   124g1411R191


You are at Part 3, for complete information see

Part 1 CHG Introduction  -  2 About Congenital Hypothyroid and 4 CHG-4 Testing Cost, by Dr. Fyfe


and have your veterinarian to report any confirmed occurrence of Congenital Hypothyroidism With Goiter (CHG) directly to Dr. John Fyfe at MSU.


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