T4
T4 is a hormone that is produced by the thyroid gland and is important for the metabolism. If your dog has too little or too much T4, this can lead to various health problems. In this blog post, you can find out more about the function, measurement and treatment of T4 in dogs.
What is T4 and how does it work?
T4 stands for thyroxine, a thyroid hormone consisting of four iodine atoms. T4 is produced in the thyroid gland and released into the blood. There it binds to proteins that transport it to the target cells. In the cells, T4 is partially converted into T3, which has a stronger effect than T4. T3 and T4 influence your dog's metabolism, growth, development and body temperature.
How is T4 measured?
To determine your dog's T4 level, a vet must take a blood sample and analyze it in the laboratory. The total T4 value is usually measured, i.e. the sum of the free T4 and the T4 bound to proteins. However, the total T4 value can be influenced by various factors such as age, breed, medication or other illnesses. It is therefore sometimes necessary to also measure the free T4 value, which only shows the unbound T4 in the blood. The free T4 value is more accurate, but also more expensive than the total T4 value.
What are the normal T4 levels in dogs?
Normal T4 levels in dogs can vary depending on the laboratory, measurement method and reference range. In general, the following values are considered normal:
- Total T4: 15-67 nmol/l
- Free T4: 7-40 pmol/l
However, these values may vary depending on your dog's age, breed and sex. For example, older dogs tend to have lower T4 levels than younger dogs. Also, some breeds such as Greyhounds or Irish Setters have naturally lower T4 levels than other breeds.
What does it mean if the T4 level is too low or too high?
If your dog's T4 level is too low, this is called hypothyroidism or underactive thyroid. This means that the thyroid gland is not producing enough hormones or that the hormones are not working properly. The most common causes of hypothyroidism are an autoimmune disease, in which the immune system attacks the thyroid gland, or atrophy, in which the thyroid gland shrinks. Hypothyroidism can lead to the following symptoms:
- Weight gain
- lethargy
- hair loss
- skin problems
- Sensitivity to cold
- Susceptibility to infections
- Behavioral changes
The treatment of hypothyroidism consists of the lifelong administration of synthetic thyroxine (L-thyroxine), which compensates for the hormone deficiency. The dosage must be adjusted individually and checked regularly.
If your dog's T4 level is too high, this is known as hyperthyroidism. This means that the thyroid gland is producing too much hormone or that the hormones are having too strong an effect. The most common causes of hyperthyroidism are a thyroid tumor or an overdose of L-thyroxine. Hyperthyroidism can lead to the following symptoms:
- Weight loss
- restlessness
- palpitations
- panting
- vomiting
- diarrhea
- Eye problems
The treatment of hyperthyroidism depends on the cause. If a thyroid tumor is present, surgery, radioiodine therapy or chemotherapy may be necessary. If there is an overdose of L-thyroxine, the dosage must be reduced or discontinued.
T4 is an important hormone for your dog's metabolism. To determine your dog's T4 level, a vet will need to carry out a blood test. If the T4 level is too low or too high, this may indicate a thyroid disorder that needs to be treated.
The authors assume that a veterinarian should be consulted if an animal is ill and that medication should only be taken after consultation with a doctor or pharmacist. Only an individual examination can lead to a diagnosis and treatment decision.
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