Dogs' thyroid levels are made up of 5 hormones and can fluctuate depending on age, breed and gender. The measurement method, temperature, health as well as the time of day and year can also influence thyroid hormones.
This also explains why you find numerous different reference values in the literature. Below you will find the averaged thyroid values in tabular form:
HormonesReference rangeUnitT41.3 – 4.5μg/dlfT40.6 – 3.71ng/dlT330 – 200ng/dlfT32.41 – 5.99pg/mlcTSH0.00 – 0.60ng/ml[1]
In some cases, the reference values are also given in other units. Below you will find the median to better compare your results:
HormonesReference rangeUnitT418.02 – 51.48nmol/lfT47.7 – 40.00pmol/lT30.68 – 2.20nmol/lfT32.92 – 6.36pmol/lcTSH0.00 – 0.60ng/ml[2]
In any case, you should contact your veterinarian, who is also familiar with the measurement procedures in the laboratory, to evaluate these result tables.
Typically, dogs' T4 thyroid levels are between 1.3-4.5 μg/dl, fT4 levels are between 0.6-3.71 ng/dl, and T3 levels are between 30-200 ng/dl Values for fT3 between 2.41-5.99 pg/ml and values for cTSH between 0.00-0.60 ng/ml.
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Influencing factors
The following factors explain why there can be large differences when comparing different laboratory values:
In puppies, the thyroid value “T4” is around 2-5 times higher up to the 4th month of life. Even in the growth phase, this value is usually still increased.
When fully grown, the hormone usually drops to the reference values given above. In old age, the values can also drop lower. [3]
What is meant here by race is primarily the difference in size. This is because small breeds tend to have higher T4 levels and large dogs tend to have lower T4 levels.
In contrast, the T3 levels of medium-sized breeds are usually higher than those of small or large dogs. This also shows how complex hormones are.
This point is heavily debated in the literature. There are said to be big differences between male dogs and female dogs, especially when it comes to thyroid levels T4 and fT4.
Female dogs usually have significantly increased values compared to male dogs. In addition, an increased estrogen level is said to greatly reduce the thyroid hormones in the table. [4]
It has already been proven in humans that there is a connection between the time of day and year and thyroid levels. In dogs it is only suspected.
In most cases, the dog's thyroid levels are determined using ELISA (“Enzyme-linked Immunosorbent Assay”) or CIA (“Chemiluminescent Immunoassay”).
Depending on the laboratory, ED (“equilibrium dialysis”), GD (“equilibrium dialysis”) or RIA (“radioimmunoassay”) are also used. [5]
Both the temperature during the measurement in the laboratory and the dog's health can have a massive influence on the thyroid hormones.
Thyroid hormones can vary depending on race, gender and age. The measurement method, temperature, state of health and the time of year and day can also cause the hormones to deviate from the thyroid values in the table.
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Importance of increased values
If the dog's thyroid produces too many thyroid hormones, it is called “hyperthyroidism”. Doctors refer to this as “hyperthyroidism”.
The four-legged friend's entire metabolism is boosted and runs faster than average. Typical symptoms of this are:
- Excessive thirst
- Enlarged thyroid
- Chronic diarrhea
- Increased pulse
- Hyperactive behavior
- Dog breathes very quickly
- Frequent vomiting
- Strong hunger
- shortness of breath
- Constant urge to urinate
- Excess energy [6]
Elevated thyroid levels are therefore a serious illness. In most cases it is caused by a tumor that affects the thyroid.
But medication or BARF (“biologically species-appropriate raw feeding”) are also suspected here. Surgery and medication are often necessary for treatment. [7]
If dogs have higher thyroid levels than shown in the table with the reference values, then this is called hyperthyroidism. Typically, affected dogs are very active, breathe faster and also experience digestive problems.
Importance of too low values
If too few thyroid hormones are produced in the dog's body, it is referred to as “underactive thyroid” or “hypothyroidism”.
Essentially, it has the exact opposite effect of values that are too high. Because the dog's metabolism becomes significantly slower. Typical signs here are:
- Low pulse
- Unexplained weight gain
- Occasional hair loss
- Constant skin inflammation
- Lack of motivation
- Dog sleeps a lot
- Slow breathing
- Dry and cracked skin
- Decreasing coat quality
- Coordination problems
- Dog gets cold very quickly [8]
In most cases, low thyroid levels are caused by an immune disorder. The following dog breeds are said to be most commonly affected:
- Golden retrievers
- Shetland Sheepdog
- Doberman
- Airedale Terriers
- dachshund
- Golden retrievers
- Great Dane
- cocker spaniel
- Irish Red Setters [9]
Since this type of hormonal disorder can rarely be cured, it is usually treated with medication. This means that dogs can generally lead a relatively normal life.
If the thyroid hormone test shows that the values are below the reference values in the table, then doctors speak of “hypothyroidism”. This can often be recognized by the fact that dogs are listless and sleep too much.
Thyroid values as a graphic
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