Hormone thyroxin: functions and norm

General information

The hormone thyroxin is produced by the thyroid gland. More precisely, it is produced by the follicular cells of the thyroid gland under the control of TSH, a thyroid-stimulating hormone. Thyroxin (T4) is one of two iodine-containing thyroid hormones. Triiodothionine (T3) is the second hormone. The biological activity of thyroxin is insignificant, but in the tissues it is affected by enzymes, and it is partially converted into the more active hormone, triiodothyronine.hormone thyroxin


The hormone thyroxin actively influences the work of the whole organism. Its functions are as follows:

  • stimulates lipid metabolism;

  • lowers cholesterol;

  • supports bone metabolism;

  • reduces the amount of triglycerides in the blood;

  • improves calcium absorption by the body;

  • stimulates the central nervous system.

The weight of a person depends on the level of thyroxin. T4 also stimulates the production of vitamin A in the liver. In addition, thyroxin is very important for the female reproductive system. When this hormone is raised or lowered, it can be difficult to conceive and carry a child.

thyroxine hormone is normal in women

The hormone thyroxin free and common: what is the difference?

The main part of total thyroxin in the blood is bound (with transport proteins of blood plasma) and only 0.1% in the free state. When the level of transport proteins in the blood changes, the content of total T4 also changes, while the amount of free remains almost unchanged. The hormone thyroxin (T4) free is biologically more active. It is his level that shows the clinical status of thyroid status.

Thyroxine (hormone): the norm in men and women

Until forty years, the amount of this hormone in the body of women and men is about the same. After the indicators vary, the level in the female body begins to decline. During pregnancy, the hormone thyroxin increases substantially, reaching maximum values ​​in the third trimester.

Production increases in the morning (from 8 to 12). At night (from 23 to 3 hours) thyroxin is produced in a minimum amount. In addition, there is an increased concentration of the hormone in the body from September to February, and its content decreases from May to September.

So, what level of body content should thyroxin (hormone) have? The norm in women is 100-120 nmol / l, the same indicators in men. These values ​​are almost unchanged throughout life.In the period of menopause in the female body there are major changes, at this time thyroxin (hormone) is also reduced. The rate in women of mature age can be 80-100 nmol / l. However, these indicators may increase or increase depending on the problems in the body. Deviations from normal values ​​are not always a sign of pathology. But in some cases with such changes it is necessary to take urgent measures.thyroxine hormone is reduced

Causes of elevated T4

The hormone thyroxin may be elevated as a result of high serum bilirubin levels. Also one of the reasons is obesity. In addition, thyroxin may increase due to:

  • thyrotoxic adenoma;

  • TSH-independent thyrotoxicosis;

  • nephrotic syndrome;

  • postpartum thyroid dysfunction;

  • chronic liver damage;

  • toxic goiter.

You should know that taking certain medications can increase the level of the hormone T4, namely the means "Aspirin", "Furosemide", "Amiodarone", "Tamoxifen", "Propthiouracil", "Propranolol", "Levothyroxine", "Danazole".

The increased symptoms of thyroxin are manifested by the following symptoms:

  • heart palpitations and high blood pressure;

  • headaches;

  • increased body temperature for a long time;

  • increased appetite;

  • frequent urination;

  • loose stools;

  • hand and eyelid tremor;

  • emotional instability, which is characterized by excessive excitability, mood swings, tearfulness, sleep problems;

  • irregular menstrual cycle;

  • shortness of breath;

  • brittle nails.

growth hormone and thyroxin

What contributes to lowering T4?

The hormone thyroxin can be lowered after surgery, rapid weight loss. Also, inflammation in the hypothalamus or pituitary, traumatic brain injury, Sheehan syndrome also leads to a decrease in the level of T4. The hormone content is also reduced when using drugs, anabolic steroids, anticonvulsants, thyreostatics. In addition, the level of thyroxin reduces the intake of oral contraceptives and the lack of iodine in the body.

With reduced thyroxine, symptoms such as:

  • frequent cramps;

  • muscle weakness and fatigue;

  • sleeplessness at night and daytime sleepiness;

  • slow thinking;

  • pallor of the skin;

  • nausea;

  • decreased appetite;

hormone thyroxin function

HGH and hormone thyroxine

Today, professional athletes often take growth hormone for a quick set of muscle mass and burning excess fat. However, in the course of numerous studies it was found that the use of the drug as the sole pharmacological agent does not give tangible results. In addition, experiments have shown that a significant fat burning effect or a significant increase in muscle mass is possible only if the T4 level in the body is normal.

As mentioned above, the hormone thyroxin is produced in greater quantities than triiodothyronine. But under the influence of certain T4 enzymes (not all, of course) turns into triiodothyronine. Growth hormone in such a transformation plays a role, providing a stimulating effect. This to some extent explains its fat burning effect.

For a pronounced physiological effect of thyroid hormones, normal or elevated levels of growth hormone in the body are necessary. Also, for the harmonious work of the latter requires a normal amount of thyroid hormones. It follows that growth hormone and thyroxin have a direct effect on the secretion of each other.

How to prepare for testing?

To determine the level of thyroxin, certain studies are required, which must be prepared in advance. A month before the tests, you should refuse to take any hormones, in particular thyroid hormones. A few days before the study, it is required to exclude medications containing iodine. The day before blood collection, even minimal physical exertion and any stresses should be completely eliminated. The ban also applies to smoking and alcohol intake.

It is best to do research in the morning and on an empty stomach. The time interval between the analysis and the last meal should be at least 6 hours.thyroxin homo norm

How does the level of T4 in the course of pregnancy?

If the hormone thyroxin is outside the norm, then this can affect the course of pregnancy, its outcome, and the condition of the baby. With the timely diagnosis of any thyroid gland ailments and the implementation of appropriate corrective actions, pregnancy can be preserved (if the ailment was detected in a pregnant woman) and planned.

With a pronounced endocrine pathology, the possibility of becoming pregnant significantly decreases.As a rule, such deviations lead to impaired fertility and infertility.

One of the most frequent diagnoses associated with the thyroid gland is an enlargement of this organ, which is more commonly known as a goiter. However, the doctor must take into account that changes in the thyroid gland occur during pregnancy. Therefore, the diagnosis of this organ is not only hormonal research, but also in ultrasound. In addition, a fine needle aspiration biopsy procedure may be required.hormone thyroxin is elevated


Disruption of the hormonal background is extremely dangerous and can trigger the development of serious diseases. If any of the above symptoms are detected, you should contact an experienced specialist and undergo a thorough examination. The content of the hormone thyroxin in the body should be checked at least once every six months. However, it is worth remembering that any medical intervention should be highly qualified. Be attentive to your health and react promptly to the slightest deviations.

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