CHOICE OF EXAMS AND INTERPRETATIONS
Thanks to the new technologies available in veterinary medicine and which we offer to you as a world exclusive, we can redesign the diagnosis of canine hypothyroidism. In this article, we present a summary of thyroid profile, with some key information for a correct interpretation.
When do you suspect hypothyroidism in dogs?
Productive thyroid deficiency usually results from a progressive immune-mediated disease. The symptoms of hormonal deficiency are numerous, different from dog to dog and progressive like gravity. The most common are lethargy, inactivity, weight gain, cold intolerance, dermatological disorders, and recurrent infections. Less common is a general weakness, incoordination, cardiovascular changes, infertility, and epilepsy.
It must be remembered, however, that the "typical" picture (dermatological lesions + alterations linked to the reduced metabolic rate) occurs only in some subjects and always belatedly. Even the most common laboratory alterations, such as non-regenerative anemia and hyperlipemia, may be lacking. The presence of gastrointestinal alterations, in particular, chronic diarrhea, is frequent.
The conclusion is that hypothyroidism must be taken into consideration when the dog has disease states that involve the skin and immune defenses and digestive, cardiovascular and neurological function, particularly when an immune-mediated origin is detected for this conditions.
What are the difficulties in diagnosing hypothyroidism?
The most common type of hypothyroidism in dogs is the primary form, with progressive gland atrophy and production deficiency in the terminal phases. Traditionally, the diagnosis was based on the serum determination of total T4 (T4 bound to transport proteins, tT4) and free T4 (free T4, fT4) concomitant with the determination of the Thyroid Stimulant hormone (TSH). The expected result in case of primary hypothyroidism is a serum TSH higher than the reference interval (as an expression of the pituitary stimulus in the presence of chronic hormonal deficiency) and fT4 and tT4 lower than the interval.
In clinical practice, on the other hand, this pattern (TSH increased, and fT4 decreased) unfortunately is not always found:
1) As demonstrated in experimental models, the TSH tends to "re-enter" in the reference interval with the chronicization of the disease and the finding of thyroid profiles with decreased fT4 and normal TSH
2) Many therapies and in general a state of disease (in particular if of an inflammatory nature) are able to reduce the quantity of serum tT4 and also of fT4 (although this analyte is less sensitive to concomitant pathologies and to therapies). Once again, the pattern will be decreased by tT4 / fT4 and normal or decreased TSH. The problem is that a hypothyroid dog is very often treated with drugs, for example, antibiotics and a state of illness is also frequent, and therefore the degree of confusion and the diagnostic difficulty will be maximum.
What is the thyroid profile for?
Thyroid profile helps to rule out the presence of thyroid diseases. In addition, this study offers the health professional (general practitioner, endocrinologist) a way to assess the patient's treatment and the evolution of the disease.
An important part of the thyroid profile test is the analysis of the thyroid stimulating hormone (TSH), which is produced by the pituitary gland that is the size of a pea and is located at the base of the brain. What is the thyroid profile for?
It helps to rule out the presence of thyroid diseases. In addition, this study offers the health professional (general practitioner, endocrinologist) a way to assess the patient's treatment and the evolution of the disease.