Congenital Hypothyroidism (CH)
Primary congenital hypothyroidism (CH) is an inherited disease affecting cats. The disease is caused by an impairment of the biosynthesis of hormones (dyshormonogenesis). Congenital Hypothyroidism in cats has similarities with the same disease in human.
Typical clinical signs in cats include disproportionate dwarfism, growth retardation and mental dullness. Thyroid blood tests show a combination of low concentrations of serum total thyroxine (T4) and high concentrations of thyroid-stimulating hormone (TSH). Other symptoms include the presence of a goitre, constipation, and delayed tooth eruption. Most affected cats have bilateral enlargement of both thyroid lobes, and, most, but not all, affected cats have a palpable goitre (presumably because of thyroid hyperplasia).
Affected cats are usually diagnosed as early as 6-8 weeks.
A variant in the TPO gene has been identified to be associated with symptoms of Congenital Hypothyroidism in cats. The variant has an autosomal recessive trait of inheritance.
The variant has so far been found in 15 breeds, namely the Balinese, Birman, British Longhair, British Shorthair, Chartreux, Domestic Shorthair, Domestic Medium Hair, Domestic Longhair, Exotic Shorthair, Main Coon, Norwegian Forest Cat, Oriental Shorthair, Russian Blue, Siberian, and Sphynx.
