Blood test for T3

The thyroid gland produces various hormones necessary for the normal and full functioning of the human body. The most basic of these are the hormone triiodothyronine, best known as the T3 hormone, and thyroxine, the T4 hormone.

Triiodothyronine is formed during the synthesis of thyroxine, when the T4 hormone loses one of its molecules. Thus, T3 consists of only three iodine molecules, which makes it at least ten times more active than T4.

It is by the amount of hormones produced by the thyroid gland that one can judge how stable and normal it functions. And since the thyroid gland has a great influence on the activity of many important organs and systems, its correct operation is very important for the full functioning of the entire human body.

What is the T3 hormone and its functions

Triiodothyronine exists in the human body in two forms: free and bound. The combination of these two forms forms the total triiodothyronine. Such a hormone is formed not only during the breakdown of thyroxin, but also in a certain amount is produced by the thyroid gland in its finished form. After that, in the blood plasma, most of the T3 is bound by albumins, globulins and prealbumins. It is these proteins that transport hormones to different places in the body. But just the part that does not contact with such proteins is called free triiodothyronine. Most often, they take an analysis for free, and in some cases for the total hormone T3, since then you can see a more complete picture of the ongoing changes in the hormonal background.

T3 thyroid hormone contributes to the normalization of energy metabolism in the human body, in other words, it receives energy from food and helps its expedient expenditure.

One of the important functions of triiodothyronine is to ensure the normal physical development of the internal organs and systems of the embryo, so it is quite important to control the level of T3 in pregnant women, as well as in those who plan to have a baby.

In addition, triiodothyronine has a significant effect on the central nervous system. Therefore, an increase in the blood of such a hormone significantly increases nervous excitability. People suffering from thyrotoxicosis are very easy to piss off, they are irritable, quick-tempered and extremely emotional.

However, the most basic role of the analysis for the T3 hormone is the diagnosis of possible pathological changes in the thyroid gland and disruption of the endocrine system as a whole.

Other functions of the T3 hormone include:

• stimulating the production of retinol by the body;
• participation in metabolic processes;
• improved metabolism;
• normalization of heart rate;
• lowering the level of bad cholesterol in the blood;
• normalization of nervous processes;
• removal of overexcitability;
• active participation in cell regeneration;
• ensuring cellular respiration of internal organs and tissues.

Indications for the appointment of a blood test for T3

A blood test for the level of triiodothyronine in the body is necessary in order to track and diagnose possible pathologies of the thyroid gland and the endocrine system. It is also prescribed in the case when the patient has symptoms of hyperthyroidism – a significant increase in the content of thyroid hormones.

An analysis for total T3 is also necessarily included in hormonal screening of the thyroid gland in such conditions:

• tendency to puffiness;
• unreasonable change in the patient’s weight;
• dysfunction of the pituitary and thyroid glands;
• painful menstruation;
• menstrual cycle disorders;
• severe symptoms of PMS.

You should also be aware that in some diseases, such as thyroid adenoma or toxic nodular diffuse goiter, formations may appear that additionally produce the hormone T3, which ultimately leads to T3 toxicosis.

Then such an examination is prescribed in order to check the effectiveness of the treatment received by the patient.

Preparation and procedure

The hormonal background of a person is very sensitive to many different factors, which is why proper preparation for taking an analysis for hormones is very important.

For the most reliable results when testing blood for free and total triiodothyronine, you need to follow a few simple rules:

1. Donate blood in the morning and always on an empty stomach.
2. On the eve of the test, refuse to exercise.
3. The day before the procedure, avoid fatty foods and alcoholic beverages.
4. Stop taking any medications. If the patient is undergoing treatment, then the analysis must be taken a week after its completion.
5. Women who take oral contraceptives at the time of the test should stop taking the drug, replacing it with non-hormonal methods of contraception.

Blood sampling for hormonal studies is carried out in the laboratory using sterile disposable instruments. This analysis is carried out by direct chemiluminescent immunoassay.

It is advisable for the patient to sit completely still for five to ten minutes before donating blood in order to improve the results of the examination.

Norms for general T3

The interpretation of the results of the analysis should be carried out by the attending physician; it is not worth deciphering the data yourself, even though the necessary standards are usually indicated on the standard forms. The specialist will help to correctly process the results, based not only on the given norms, but also on the patient’s history, his individual characteristics and other studies. Based on all this, the necessary treatment is prescribed.

It should also be taken into account that the norms of the hormone, reagents and equipment in each laboratory can differ significantly, therefore it is necessary to carry out both treatment and diagnosis in the same clinic.

The norm of total triiodothyronine for adult women and men is from 0,89 to 2,44 nmol / liter. For children, the standards are slightly higher and amount to 1,74 – 2,91 nmol / liter.

In this case, it should be borne in mind that there are several factors that can significantly affect the final result of the analysis:

• taking drugs that reduce the level of T3 in the blood: aspirin, furosemide, androgens, anabolics, cimetidine, amiodarone, atenolol and others;
• taking drugs that increase the level of T3 in the blood: lithium preparations, tamoxifen, estrogens, methadone and clofibrate; period of pregnancy;
• liver dysfunction, liver disease;
• advanced age of the patient;
• myeloma;
• somatic diseases in severe form.

Increasing the level of T3

With an increased level of triiodothyronine, thyrotoxicosis is diagnosed, accompanied by the following pronounced symptoms:

• sleep disorders, insomnia;
• palpitations, heart rhythm disturbances;
• constant fatigue and increased fatigue;
• emotional lability, increased aggression;
• significant weight loss for no apparent reason;
• menstrual irregularities, breast enlargement in men;
• frequent urination, digestive disorders.

In this case, you should be aware that if a significant increase in the hormone T3 is diagnosed with a normal level of other endocrine hormones, it is considered to be a false positive result.

An increase in the rate of triiodothyronine in the body indicates the presence of diseases such as thyroiditis – an autoimmune thyroid disease, hyperthyroidism, thyroid adenoma, Graves’ disease – poisoning of the body with its own thyroid hormones, postpartum thyroid dysfunction, Pendred’s syndrome – an increase in the size of the thyroid gland at the genetic level.

The list of diseases also includes nephrotic syndrome – a kidney disease characterized by severe swelling, independent TSH thyrotoxicosis or isolated T-thyrotoxicosis, resistance to endocrine hormones.

Decrease in T3 level

A decrease in the level of triiodothyronine in the body indicates problems with the secretory function of the thyroid gland. This is characterized by a decrease in the level of other endocrine hormones. Symptoms with a decrease in T3 in the body are as follows:

• decrease in body temperature, characteristic of a breakdown;
• development of a convulsive syndrome;
• increased fatigue, drowsiness, lethargy;
• muscle weakness and weakness of ligaments;
• violation of potency;
• nausea and vomiting, loss of appetite, frequent constipation;
• increased swelling.

In some cases, a slight decrease in triiodothyronine is not a pathology. For example, in the third trimester of pregnancy, this phenomenon is considered the norm.

In all other cases, these symptoms are characteristic of such diseases:

• thyroid insufficiency;
• diffuse or nodular toxic goiter;
• renal failure, impaired renal function, cirrhosis of the liver;
• nervous form of anorexia;
• starvation, exposure to diets;
• iodine deficiency in the body;
• thyroid surgery.

Summing up

A blood test for T3 is prescribed by the attending physician if there is a suspicion of a violation of the thyroid gland or the endocrine system. Such a diagnosis is quite complicated, therefore it is extremely important to properly prepare for it, since even the slightest deviation can lead to false results. It is necessary to carry out such an analysis in specialized laboratories, where there is advanced modern equipment that will eliminate various inaccuracies.