Thyroid values ​​• What do TSH, T3 & T4 mean?

The thyroid gland (glandula thyreoidea) is a small, butterfly-shaped organ located in the front of the neck. It is involved in the production of various hormones and influences important metabolic processes, personality and psyche, sexuality and fertility and even the growth of skin, hair and nails.

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Thyroid Facts – What You Should Know

If the gland doesn’t work properly, it can have far-reaching consequences. Thyroid diseases are therefore a serious problem. Around every third adult in Germany suffers from pathological changes in the organ.

How the hormones TSH, T3 and T4 interact

The thyroid produces the hormone thyroxine from iodine and protein components. She gives this in two forms,

• the Tetraiodothyronine, also L-thyroxine or abbreviated T4,
• and Triiodothyronine (T3)

to the blood. With the two messenger substances, the mini-organ controls almost all vital functions in the body: the metabolism, heart and circulation, stomach and intestines, nerves and muscles.

How much or how little T3 and T4 the thyroid produces is determined by another hormone, the Thyroid-stimulating hormone TSH (also thyrotropin) determined. This is produced in the pituitary gland and transported to the thyroid gland via the blood.

• If the level of the two hormones T3 and T4 is sufficient, the release of further TSH is inhibited;
• if the values ​​fall, more TSH is released again.

This process is also called the thyrotropic control loop, which – if everything works as desired – ensures the balance of the three important messenger substances.

TSH as the central thyroid value

The individual values ​​for TSH, T3 and T4 indicate whether this mechanism is running normally and how the thyroid gland itself works. The relationship between individual values ​​can also be relevant. The most important is the TSH value, it is also called the primary or central thyroid value. If it is true, it can be assumed that the thyroid is working normally.

T3 and T4 are both bound and free in the body. Only as free Tetraiodothyronine (fT4) and free Triiodothyronine (fT3) they are important as messenger substances and are important for diagnosis. They are also known as peripheral thyroid levels.

Determination of TSH, T3 and T4 in diagnosis

Whenever certain Symptoms of a thyroid disorder indicate, the values ​​for the thyroid hormones TSH, T3 and T4 should be determined.

The following symptoms can be attributed to a Hyperfunction (Hyperthyroidism):

A Subfunction (Hypothyroidism) can show through:

• Fatigue and listlessness
• Sensitivity to cold
• Muscle weakness
• brittle nails and dry skin
• lack of concentration
• increased need for sleep
• Weight gain
• constipation

The values ​​are also determined if acute or chronic inflammation of the thyroid gland, Graves’ disease or an enlarged thyroid gland is suspected.

Thyroid values ​​for therapy control

In the case of a thyroid disease that has already been diagnosed, TSH, T3 and T4 are determined to check the administration of medication and to monitor the course of therapy. Before an operation under anesthesia or a radiological examination with a contrast medium containing iodine, the TSH value is also checked to determine whether the thyroid is able to cope with the iodine intake.

The blood values ​​for TSH, T3 and T4 are determined in the blood serum. It is not a standard test for small or large blood counts. In newborns, as part of the newborn screening, the thyroid values ​​in the blood are measured on the third day of life in order to detect congenital hypothyroidism and, if necessary, treat it at an early stage and thus prevent developmental disorders in the brain and organs.

Normal values ​​for TSH, T3 and T4

The normal levels for thyroid hormones are the same for men and women. The following values ​​indicate the normal range for adults:

Important to know about laboratory results: Values ​​can deviate from the specified normal value depending on the age or the chosen laboratory method. In children, higher normal TSH values ​​apply. In newborns they are up to 20 µU / l. Even in pregnant women, values ​​can occur slightly above the reference values.

With hormone replacement therapy or for Goiter treatment (Therapy of goiter) the normal value for TSH is 0.3 to 1.2 mU / l.

What do high or low thyroid levels mean?

If the thyroid values ​​deviate from the normal value, this can have different causes. The following table shows the most important reasons for high and low levels of TSH, T3 and T4. The relationship between the values ​​can also be important when diagnosing the diseases. For example, the TSH value is increased with hypothyroidism, while the values ​​for triiodothyronine (fT3) and thyroxine (fT4) are usually lower.

Further diagnosis and treatment for abnormal thyroid values

If a blood test reveals changed values ​​for TSH, thyroxine and triiodothyronine, the exact causes can be narrowed down with further laboratory values. An ultrasound examination (sonography) of the thyroid gland examines the structure of the organ and any changes in the tissue. With the scintigraphy, the attending physician determines how well the individual areas of the organ can absorb and process iodine.

In the case of an underactive thyroid, the hormone deficiency is usually compensated with medication. A frequently used active ingredient is Levothyroxine (L-thyroxine), which corresponds to the thyroid hormone tetraiodothyronine (T4). In order to determine the correct dosage of thyroid hormones, the blood values ​​must be checked regularly by a doctor and the thyroxine dose adjusted if necessary.