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Slow functioning thyroid gland

General info

An slow functioning thyroid, also called hypothyroidism, is the most common thyroid disorder in dogs. The normal thyroid gland is responsible for the production and release of sufficient thyroid hormones, which are responsible for regulating various metabolic processes in the body. In the case of hypothyroidism, less thyroid hormone is produced and/or secreted. This gives rise to vague clinical complaints, among which decreased activity, weight gain and skin complaints are the most common.




Lazy dog

Most common causes for hypothyroidism in dogs are lymphocytic inflammation of the thyroid gland or a reduced thyroid gland (atrophy). Less common causes are congenital hypothyroidism and acquired central hypothyroidism.

The diagnosis is often based on the presence of clinical symptoms, physical examination and determination of thyroid hormone (total T4) and thyroid stimulating hormone (TSH) in the blood. Typical blood test abnormalities are a decreased total T4 and an increased TSH.

Sometimes the total T4 and/or the TSH are normal, so that the diagnosis is less obvious. This requires additional examinations such as a TSH stimulation test or scintigraphic examination of the thyroid gland. Determinations of other types of thyroid hormone in the blood are not routinely performed.

Hypothyroidism is treated through thyroid hormone supplementation. Therefore, the use of veterinary preparations is important. Upon initiation of medication, a rapid improvement of the clinical symptoms is noted.


Thyroid function should be monitored in the blood through total T4 to determine whether thyroid values have normalized with the medication. This blood test is usually performed 3-4 hours after the administration of the medication.

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