Congenital hypothyroidism with goiter / CHG (TPO-related) - Rat Terrier and Toy Fox Terrier

What does this test analyse?

This genetic test analyses the TPO variant c.331C>T in Rat Terrier and Toy Fox Terrier. The condition is known as congenital hypothyroidism with goiter, CHG and goitrous congenital hypothyroidism.

Why is this test important?

TPO encodes thyroid peroxidase, an enzyme needed to bind iodide to thyroglobulin and produce thyroid hormone. Puppies with two copies of the tested variant can fail to produce enough thyroid hormone early in life. Possible consequences include poor growth, lethargy, poor nursing, delayed opening of the eyes and ear canals, abnormal coat or skin development, an enlarged thyroid gland in the neck and sometimes skeletal changes. When goiter is present, neck swelling can also affect swallowing or breathing.

Practical value of this test

• Breeders can distinguish clear dogs, carriers and genetically affected dogs before planning matings.
• The result helps avoid carrier x carrier matings and directly lowers the risk of puppies with this serious congenital thyroid disorder.
• Valuable carriers can remain in the population responsibly by combining them only with clear partners.
• In young puppies with poor growth, neck swelling, lethargy or delayed development, the test provides a concrete genetic explanation that supports early follow-up.
• The test helps separate inherited congenital hypothyroidism from other causes of low thyroid values or delayed development.

Inheritance and interpretation

The trait is autosomal recessive. C/C means the tested variant was not detected. C/T means carrier: one copy does not cause this variant-linked form, but the dog can pass the variant on. T/T causes congenital hypothyroidism with goiter and is reported as a genetically affected result.