Congenital hypothyroidism (CH)

A genetic variant in the thyroid peroxidase (TPO) gene causes primary congenital hypothyroidism in cats. Affected cats show disproportionate dwarfism. Some cats have obvious growth retardation while in others it is less noticeable. Other signs can be goiter with bilateral enlargement of both thyroid lobes, mental dullness, constipation and delayed tooth eruption. Serum Total T4 concentrations are low to low-normal while TSH concentrations are abnormally high. Congenital hypothyroidism is typically diagnosed at a young age. Supplementation with L-T4 leads to an clinical improvement, as well as an increase in serum T4 and a decrease in TSH concentrations.