Breeds Affected: Rat and Toy Fox Terriers
Samples Accepted: Blood, Buccal Swabs
Disease Information: Congenital Hypothyroidism is also known as Congenital Hypothyroidism with Goiter. Affected pups exhibit growth retardation, delayed tooth eruption, delayed eye and ear opening, lethargy, hair coat abnormalities, thickened skin, and goiter. The disease can be fatal without early diagnosis and treatment.
Inheritance Information: Congenital Hypothyroidism is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
The possible genotypes are:
N/N The dog is normal, and cannot produce affected offspring.
N/ch The dog is a carrier and can pass the allele on to approximately 50% of any offspring. If bred to another N/ch carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
ch/ch The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/ch carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/ch x N/N) without any risk of producing affected offspring. The offspring should be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/ch x N/ch) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (ch/ch) should not be used for breeding.
Test Information: This mutation test identifies a single base pair change in the TPO gene.
Fyfe, J.C., Kampschmidt, K., Dang, V., Poteet, B.A., He, Q., Lowrie, C., Graham, P.A., Fetro, V.M. : Congenital hypothyroidism with goiter in toy fox terriers Journal of Veterinary Internal Medicine 17:50-7, 2003. Pubmed reference: 12564727.
Pettigrew, R., Fyfe, J.C., Gregory, B.L., Lipsitz, D., Delahunta, A., Summers, B.A., Shelton, G.D.: CNA hypomyelination in Rat Terrier dogs with congenital goiter and a mutation in the thyroid peroxidase gene. Vet Pathol 44:50-6. Pubmed reference: 17197623. DOI: 10.1354/vp.44-1-50.
Further information is available at the Online Mendelian Inheritance in Animals website.