Congenital Dyshormonogenic Hypothyroidism with Goiter

Affected dogs may have a proportionate decrease in size compared to littermates or the presence of a goiter.

A goiter is an enlarged thyroid gland attempting and failing to produce thyroxine. Goiter may be observed as early as 3 weeks of age. Keep in mind, testing clear of this variant does not guarantee that a dog will not develop acquired hypothyroidism later in life. It’s important to have regular veterinary check-ups. Monitoring of a dog's health is key to catching and treating the first signs of age-related hypothyroidism.

Veterinarians may confirm the diagnosis by measuring increased plasma TSH associated with decreased total thyroxine (TT4) concentrations and free thyroxine (FT4) or via thyroid imaging (ultrasound or scintigraphy).

Hypothyroidism is a lifetime condition, however it can be managed medically. Affected dogs can be treated with hormone replacement (like sodium levothyroxine) and additional treatment for heart disease if needed.

Talk to your vet about your dog’s congenital hypothyroidism result, as it may influence how they monitor your dog’s thyroid function, growth, and development.

Schedule regular checkups and bloodwork to check thyroid hormone levels and make sure your dog is growing normally.

Contact your vet if you notice signs such as sluggishness, weight gain, hair loss, or changes in coat quality, as early treatment can help your dog stay healthy and active.

This variant was first described in Shih-Tzus and can also lead to dilated cardiomyopathy (DCM), thyroid ectopic tissue, and/or follicular thyroid carcinoma. Contrary to TPO enzyme defects and other forms of CH, dogs affected by this SLC5A5 variant did not exhibit typical signs of CH such as mental dullness, disproportionate dwarfism, and alopecia.

Penetrance: Congenital Dyshormonogenic Hypothyroidism with Goiter is recessive, that is, a dog requires two copies of the variant to show signs of the disease from the variant.

Gene

SLC5A5

Inheritance type

recessive

Clinical category

Endocrine

Citations

1. Soler Arias et al 2018

• Shih Tzu