In other species: chicken , dog , lesser panda , horse , goat , sheep

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 274500 (trait) , 606765 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2015

Cross-species summary: Deficiency of thyroid gland activity. Also known as Goiterous congenital hypothyroidism; Congenital hypothyroidism; Thyroid dyshormonogenesis. This disorder can be caused by mutations in different genes, and forms of the disease exist that are not inherited.

History: The occurrence of this disorder in a family of Domestic shorthair cats was reported by Mazrier et al. (2003)

Inheritance: In the family reported by Mazrier et al. (2003), autosomal recessive inhetitance was observed.

Molecular basis: By partially sequencing a strong candidate gene Morrow et al. (2006) reported the molecular basis of this disorder in Domestic shorthair cats as being very likely due to an 8bp deletion in intron 9 of the gene for the enzyme thyroid peroxidase (TPO). Further investigation by the same team identified a causal missense mutation in the TPO gene (c.1333G>A; p.Ala445Thr) (Giger et al., 2015).

Clinical features: The most common clinical feature of a cat with congenital hypothyroidism is disproportionate dwarfism. Some features of this include a large skull with shortened mandible and ears, a square trunk and short neck (with possible goitre) and limbs, delayed eruption of deciduous and permanent teeth, and occasionally kyphosis. It is also characterised by mental deficiency, and abnormalities of the central and peripheral nervous system. Other less specific features include hypothermia, anorexia, obesity, constipation, lethargy, a persistent juvenile hair coat and delayed closure of growth plates (Greco, 2006; Hermans et al., 2020)

[IT thanks DVM student Rhyanna Boyce, who provided the basis of this contribution in April 2022]

Pathology: An analysis of the biochemistry and haematology of the blood can show hypercholesterolemia, hypercalcaemia, mild non-regenerative anaemia, and low levels of thyroid hormones (T4 and THS, or thyroid scintigraphy) in a cat with congenital hypothyroidism. As thyroid hormones are key to bone development, epiphysial ossification and epiphysial dysgenesis are common features of congenital hypothyroidism. Spinal radiographs can demonstrate severely shortened vertebral bodies and open growth plates (Greco, 2006; Hermans et al., 2020; Golinelli et al., 2022)

[IT thanks DVM student Rhyanna Boyce, who provided the basis of this contribution in April 2022]

Breed: Domestic Shorthair.

Associated gene: