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Congenital hypothyroidism in cats

Metabólico · Cat

Congenital hypothyroidism is a hereditary disease in which the thyroid gland does not produce sufficient thyroid hormones from birth, usually due to a defect in hormone synthesis (iodine organification) that presents with goitre. It affects metabolism and development: kittens grow poorly, are apathetic and constipated and have altered skin and coat. Without levothyroxine treatment, growth retardation and cognitive impairment become irreversible, but with early diagnosis the prognosis is reasonable.

Inheritance pattern	Autosomal recessive. Affected cats are homozygous for the variant; heterozygotes are healthy carriers.
Gene / Mutation	TPO. Main variant: c.514G>A p.(Gly172Arg) (NC_058370.1:g.139592392C>T; formerly c.430G>A p.(Gly144Arg)), in British shorthair, Russian Blue, domestic shorthair/mediumhair/longhair and other breeds (Van Poucke et al., 2022). Historical variant: c.1418G>A p.(Ala473Thr) (formerly c.1333G>A p.(Ala445Thr); NC_058370.1:g.139582244C>T), described in domestic shorthair cats (Giger et al., 2015); it was not detected in the cases of Van Poucke et al. (2022).
Penetrance	In homozygosity the disease manifests in the first months of life with high penetrance: all affected cats in the study by Van Poucke et al. (2022) were homozygous for the c.514G>A variant. The severity of the condition varies. Heterozygotes are clinically healthy carriers.
Code	lted
Turnaround time	7 days
Price	36,05 €

Incidence

Van Poucke et al. (2022) found the c.514G>A variant in 15 breeds, with an estimated allele frequency of 9 % in the undiagnosed cats analysed; all affected cats were homozygous. The breeds include British shorthair, Russian Blue and domestic shorthair, semi-longhair and longhair populations. Breed-specific frequencies are scarce: limited data.

Breeder management

- Test breeding animals of the included breeds: identifies clear and carrier animals.\n- Do not mate two carriers together.\n- A carrier may be mated to a clear animal; test the offspring intended for breeding.\n- In kittens with retarded growth and lethargy, request a full thyroid profile (total and free T4, TSH) before ruling out other causes.

Specialist notes

Differential diagnosis with pituitary dwarfism, malnutrition, other congenital bone diseases and feline hepatic lipidosis. Laboratory findings show low T4 with elevated TSH and frequently high cholesterol; thyroid scintigraphy is compatible with a defect in iodine organification. Levothyroxine treatment is effective if started early: the growth and activity response within a few weeks confirms the diagnosis. Monitor for overdosing (tachycardia, weight loss, restlessness) with periodic hormone checks. The main variant c.514G>A and the historical variant c.1418G>A must be distinguished, as they are not equivalent.

References

1. Van Poucke M, Van Renterghem E, Peterson ME, et al. Association of recessive c.430G>A (p.(Gly144Arg)) thyroid peroxidase variant with primary congenital hypothyroidism in cats. J Vet Intern Med. 2022;36(5):1597-1606. PMID: 36054182.
2. Lyons LA. DNA mutations of the cat: the good, the bad and the ugly. J Feline Med Surg. 2015;17(3):203-219. PMID: 25701860.
3. Gallego-Munevar C, Carrillo-Godoy N, Rondón-Barragán IS. Molecular detection of a novel mutation in the TPO gene associated with congenital hypothyroidism in a cat: Case report. J Adv Vet Anim Res. 2024;11(4):1030-1036. PMID: 40013294.
4. OMIA:000536-9685. Hypothyroidism, congenital in Felis catus. https://omia.org/OMIA000536/9685/

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