Why the hormone T4 free( thyroxin) is lowered

Tetriodothyronine is a hormone produced by the thyroid gland and composed of 4 iodine molecules. Determining its level is an important measure in the diagnosis of endocrine diseases. Alas, not everyone knows about its properties and possible deviations from the norm. The high level of T4 is a serious anomaly, as women who were taking medications based on it to reduce their body weight could see.

An excess of substance leads to unpleasant symptoms, and what happens to the human body if the free T4 is lowered? What does it mean, what does it mean and is it worth worrying? Let's understand in order.

Common causes and main symptoms of abnormalities

What does it mean if thyroxin free is lowered? Of course, it doesn’t say anything good, especially if the warning signs were suddenly added to the general malaise:

  • is constant fatigue and lethargy;
  • memory loss;
  • chill sensation;
  • brittle nails;
  • hair loss;
  • skin peeling;
  • edema formation on the face, limbs, neck, abdomen;
  • sharp weight jump;
  • menstrual disorders.

Note. Low T4, accompanied by the above symptoms, can lead to serious consequences, up to the onset of a coma. To avoid this, it is necessary to pay attention to the warning signs and seek medical help immediately.

Causes of T4 reduction

If the T4 hormone is low, then before you do something, you need to find out the causes of the deviation. They are often associated with abnormalities in the thyroid gland, as indicated by the symptoms discussed above. Consider the most common anomalies that lead to a decrease in tetraiodothyronine levels.

  1. Removal of the thyroid gland. If T4 free is below normal after surgery to remove part or all of the thyroid, then a decrease in tetraiodothyronine level is a temporary phenomenon. When all the recommendations of the doctor are fulfilled, the anomaly will not be able to harm human health.
  2. Hypothyroidism. Low T4 in normal TSH is most common in hypothyroidism. This disease is characterized by a deficiency in the production of thyroid hormones. May occur for various reasons. Often found in pregnant women.
  3. Thyroid fibrosis is another cause of reduced T4 free. Other neoplasms - benign or malignant - may also affect the level of a substance. But they can be identified only during ultrasound.
  4. Lack of iodine leads to low T4 free with normal TSH.The same thing happens when hypothyroidism was treated by using radioactive iodine.
  5. Taking thyrostatics and thyrotoxic drugs is another reason why T4 is free low.

All these abnormalities are associated with the development of primary hypothyroidism. However, with congenital anomalies, tetraiodothyronine levels will also be low.

Low T4 in pregnant women

What does it mean if T4 free is lowered, and can there be other reasons for such a deviation? Several factors exist, and they may be as follows.

  1. Myxedema. In a literal sense, the word translates as "slimy edema."If T4 free is below normal due to the development of myxedema, this means that the tissues and cells of the whole body do not receive the required amount of pancreatic hormones. This is an extremely dangerous deviation, which is the extreme, clinically expressed degree of hypothyroidism. Thyrotropin
  2. is a pathology in which TSH remains normal, while T4 is lowered. The disease is characterized by the formation of a benign neoplasm in the pituitary gland in violation of the normal functioning of the thyroid gland. As a result, it cannot produce enough hormones for the whole body to work.
  3. Protein Deficiency. If free thyroxin is lowered, this may indicate an acute protein deficiency. Like iodine deficiency, such a deviation is a serious anomaly that can lead to unpleasant consequences. For this reason, the balance of protein in the body must be regularly replenished.

The reasons why T4 free is lowered, women in an “interesting position” are particularly interested. And it is not surprising, because the causeless, at first glance, decrease in the level of this substance cannot but cause concern. But there is nothing to worry about, especially if the concentration of tetraiodothyronine has decreased in the last months of pregnancy, because the fetus growing inside the womb leads to the displacement of neighboring organs, which affects the work of the whole organism.

Naturally, sooner or later, this process will affect the thyroid gland, so if T4 is free to decrease during pregnancy, there is no need to panic, especially if the doctor himself says that there are no deviations.

Other causes and pathologies

The reduction of tetraiodothyronine levels is not the last influence:

  • bad habits;
  • autoimmune thyroiditis( Hashimoto thyroiditis);
  • goiter;
  • hypothyroidism;
  • changes in human hormones.

Briefly consider each option.

Harmful habits and T4

Extremely negative impact on the work of all organs, glands and systems is not so much smoking, as alcoholism and drug addiction. But it is precisely among drug addicts that the level of T4 is always significantly below the norm and permissible deviations from it.

Under the influence of narcotic drugs, the endocrine system is impaired, therefore, drug addicts constantly experience signs of thyroid disease: irritability, nervousness, mood swings, nervous and physical exhaustion, etc.

Changes in the hormonal background

Decreased T4 levels may result from changes in hormonalbackground occurred on the background of hormone therapy. Such a deviation is often found in women who have taken oral hormonal contraceptives for a prolonged period of time.

Thyroid dysfunction also leads to hormonal disruptions. In particular, the production of sex hormones decreases in men and women.

Note. Tetraiodothyronine level jumps can be caused by taking various medications. Even an ordinary aspirin tablet can provoke a sharp drop in the level of this substance.

Primary hypothyroidism

In primary hypothyroidism, there is a gradual increase in the concentration of TSH, while tetraiodothyronine is kept within acceptable limits. But over time, the situation begins to change, so in the late stages of the development of pathology, TSH is elevated and T4 is lowered. This is due to the fact that the human body is activated to combat the disease, beginning to intensively produce thyroid-stimulating hormone.

With a strong immune system, this process leads to the normalization of tetraiodothyronine, but if its concentration continues to decline, this is a bad sign. Such a deviation may indicate severe course of primary hypothyroidism, so it requires immediate medical intervention.


If TSH is low, but T4 is normal, this may indicate the onset of the development of toxic goiter. But such a deviation may also indicate other pathologies( for example, tumors of the hypothalamic-pituitary system), so the patient needs a complete comprehensive examination.

Autoimmune thyroiditis

Thyroiditis Hashimoto is a fairly common autoimmune pathology. Characterized by the state when the immune system begins to produce a large number of aggressive cells that destroy the cells of the thyroid system. As a rule, the disease does not pose a serious danger and is successfully treated. But do not ignore her symptoms, because she is prone to progression.

Whatever the reasons for the decrease in blood tetraiodothyronine concentration, it is not possible to determine them by yourself. Only a biochemical blood test and additional instrumental diagnostic methods will help identify the pathology and begin its treatment before it leads to serious complications and irreversible processes in the body.