Insulin-like growth factor 1. Reasons for the appearance of insulin-like growth factor. Increasing the level of FMI

Insulin-like growth factor (IGF, somatomedin C) is a hormone that is produced in the liver and muscles and is a mediator of growth hormone (somatotropic hormone, SG). Growth hormone is produced by the pituitary gland (an endocrine gland located at the base of the brain), after which most of it goes to the liver, where it stimulates the production of insulin-like growth factor. IGF from the liver enters the blood, from where, with the help of special carrier proteins, it is transported to organs and tissues, where it stimulates the development of muscles, bones and connective tissue.

The level of IGF in the blood directly depends on a person’s age. In early childhood, its concentration in the blood is low. It increases with age, reaching maximum values ​​during puberty, after which a gradual decrease in somatomedin levels occurs.

The concentration of IGF in the blood during pregnancy gradually increases with increasing gestational age.

Since the concentration of growth hormone fluctuates throughout the day (it is released unevenly into the blood, several times a day, the maximum concentration is usually determined at night), determining its level in the blood is difficult. Therefore, to assess disturbances in the production of somatotropic hormone, it is more expedient to determine the concentration of IGF, the level of which remains relatively constant throughout the day.

An insufficient amount of IGF and, as a result, growth hormone, can be caused by nutritional deficiency, kidney disease, liver disease, hypopituitarism (a disease in which there is a decrease or complete cessation of hormone production by the pituitary gland).

IGF deficiency in early childhood can lead to retarded growth and development of the child, while in adults, with a lack of IGF, a decrease in bone density, underdevelopment of muscles and changes in fat composition are usually observed.

Excessive levels of somatomedin C cause gigantism in children and acromegaly in adults. Gigantism in children involves excessive bone growth, resulting in abnormally high growth and enlargement of the arms and legs to very large sizes. Acromegaly is a disease in which there is an increase in size and expansion of the bones of the arms, legs, face, and internal organs, which often leads to heart disease and can cause death as a result of cardiomyopathy - damage to the heart muscle (myocardium) and disruption of its function.

The most common cause of increased concentrations of growth hormone (and, as a result, IGF) is a pituitary tumor, which can be surgically removed, treated with medication, or with chemotherapy. When a tumor is removed, this test is used to monitor the successful outcome of the operation (if the tumor is not completely removed, the IGF level will be increased) and to identify possible relapses.

The test determines the concentration of insulin-like growth factor (IGF) in the blood (ng/ml).

Method

The chemiluminescence immunoassay method (CHLA) is one of the most modern methods of laboratory diagnostics. The method is based on an immunological reaction, in which, at the stage of identifying the desired substance (insulin-like growth factor), phosphors are added to it - substances that glow in ultraviolet light. The luminescence level is measured using special luminometer devices. This indicator is proportional to the concentration of the substance being determined.

Reference values ​​- norm
(Insulin-like growth factor (IGF-1, somatomedin C), blood)

Information regarding the reference values ​​of indicators, as well as the composition of the indicators included in the analysis, may differ slightly depending on the laboratory!

Norm:

Indications

Presence of signs of growth hormone deficiency in children (slow growth);

Presence of signs of growth hormone deficiency in adults - reduced bone density, fatigue, unfavorable changes in fat composition, low exercise endurance (the IGF test is not specific for patients with these symptoms, since growth hormone and IGF deficiency are rarely the cause of these conditions) ;

Suspicion of low activity of the pituitary gland;

The presence of symptoms of gigantism in children or acromegaly in adults;

After surgery to remove a growth hormone-producing tumor (to confirm that it has been completely removed);

When undergoing drug or radiation therapy, which usually follows surgery to remove a tumor;

For several years after surgery to remove the tumor to control the production of growth hormone and prevent possible relapses.

Increasing values ​​(positive result)

An increased level of IGF is observed in the following conditions and diseases:

Acromegaly (a disease accompanied by enlargement of the hands, feet, skull, especially its facial part);

Itsenko-Cushing syndrome (characterized by increased blood pressure, weight gain, osteoporosis. Women experience hirsutism (male hair growth), men may develop impotence);

Kidney failure;

Pituitary tumors;

Use of medications (androgens, clonidine, dexamethasone).

Throughout life, the human body produces somatotropic hormone (GH), called growth hormone. It is produced by the pituitary gland, the part of the brain responsible for the functioning of the endocrine system.

Not only doctors are interested in the effects of somatotropin on the human body, but also weightlifters who use a synthetic analogue of this substance in the form of injections to build muscle mass and burn fat.

Back in the middle of the last century, scientists began studying somatotropin and managed to find out that growth hormone itself is not capable of affecting the cells of the body. This meant that its interaction with them must be ensured by an intermediary that transmits hormonal messages of somatotropin to the cells.

This issue was studied over the next twenty years, as a result, scientists were able to identify a whole group of intermediaries called insulin-like growth factors or somatomedins. These included:

• IGF1 (C);
• IGF2 (B);
• IGF3 (A).

But studies have shown that the only mediator involved in the delivery of somatotropin to tissue cells is the insulin-like growth factor IGF1. The remaining two substances were experimental, artificially created objects. However, the designation 1 remained behind it.

What is the significance of IGF1 for the human body, what consequences does an increase or decrease in its level cause, and how is its amount in the human blood determined?

Insulin-like growth factor is a protein similar in structure and function to insulin (a hormone secreted by the pancreas). IFR and STG are inextricably linked. Somatomedin is secreted by the liver with the direct participation of growth hormone. First, the pituitary gland produces growth hormone, which goes straight to the liver, causing it to secrete somatomedin. Within 1-1.5 hours, growth hormone is completely neutralized.

At this point, the IGF gets to work, moving from the liver into the bloodstream. It enters organs and tissues thanks to special carrier proteins. And upon arrival, it begins to have a stimulating effect on muscle, bone and connective tissue.

The greatest interest among researchers was the fact that almost every cell in the body is capable of independently producing IGF, thus replenishing the lack of the substance coming from the liver.

Somatomedin is called insulin-like growth factor 1 because of its dependence on insulin, which provides the liver with the amino acids needed to produce IGF.

At birth, a certain amount of insulin-like growth factor is already present in the baby's blood, the concentration of which increases as the person grows. The highest concentration of this substance is observed in the blood of adolescents who have reached puberty. Until the age of 40, the amount of IGF in the blood is constant. Then there is a gradual decrease. The minimum level of this substance is diagnosed at the age of 50 years.

The amount of somatotropin production in the pituitary gland directly depends on the concentration of somatomedin. The same protein also affects the production of somatoliberin, which activates the production of growth hormone. This means that when IGF levels decrease, the production of hormones by the pituitary gland increases, and vice versa. However, this balance can be disrupted due to various reasons, including poor nutrition.

Despite the relationship between IGF and growth hormone, its level is also influenced by other hormones, including insulin, sex and thyroid hormones. The increase in IGF levels occurs in proportion to the increase in the amount of these hormones. Hormones produced by the adrenal glands, for example, glucocorticoids and steroid hormones, can reduce the production of IGF.

The effect of somatomedin on the body

IGF1 has a positive effect on all muscles and tissues of the body.

1. This substance helps increase muscle mass.
2. Insulin-like growth factor strengthens the heart muscle and prevents the development of cardiovascular diseases.
3. The protein produced by the liver improves the absorption of chondroitin and glucosamine into the blood, which helps maintain youthful joints.
4. IGF1 enhances tissue regeneration. Moreover, this factor applies not only to muscle tissue, but also to nervous tissue.
5. Normal protein production slows down the aging process of the body caused by age-related changes.
6. Despite the fact that IGF is not able to increase a person’s physical endurance, it promotes the growth of muscle tissue.

Scientists have found that the life expectancy of people whose amount of insulin-like growth factor is closer to the upper limit of normal increases. And over the course of their lives, they are less susceptible to developing cardiovascular diseases.

Symptoms and causes of decreased IFR

Low levels of insulin-like growth hormone cause many irreversible side effects, which include:

• dwarfism or nanism, if children experience a lack of this protein;
• weakening of muscles and decreased functions of internal organs;
• fragility of bones, leading to fractures and other injuries;
• change in the structure of adipose tissue.

1. Cirrhosis of the liver. During the process of destruction, the liver is unable to synthesize protein.
2. Kidney diseases leading to disruption of the adrenal glands.
3. Hypothyroidism is a disease of the thyroid gland in which its function is reduced.
4. Lack of sleep leads to a decrease in the production of somatotropin, which causes the liver to synthesize somatomedin.
5. Poor nutrition and late meals have a negative impact on how growth hormone is produced.
6. Starvation and anorexia.
7. Taking hormonal drugs, in particular estrogen.

Insulin-like growth factor can be brought back to normal only by eliminating the main cause of hormonal imbalance in the body. For example, if the cause of this is hypothyroidism, then the synthesis of somatomedin can be enhanced using iodine-containing drugs or synthetic analogues of thyroid hormones, for example, thyroxine.

If the reasons for the decrease in somatomedin synthesis are poor diet or lack of sleep, then a balanced diet and adjustments to the daily routine will help eliminate it.

Symptoms and causes of increased IFR

A high concentration of insulin-like growth factor 1 in the blood is no less dangerous for human life. If the level of the hormone is elevated, this may indicate the presence of a benign tumor of the pituitary gland, which begins to rapidly synthesize somatotropin. It is the high concentration of somatotropin that leads to an increase in IGF. In this case, only surgery to remove the tumor can help. If in this case the indicator is increased, it means that the operation was ineffective.

If insulin-like growth factor is produced in excess, the following side effects occur.

1. Gigantism in children. This disease most often begins to appear when a child is 8 or 9 years old. During this period, bones begin to grow at an accelerated rate, and their growth is disproportionate. It is very important not to confuse gigantism with hereditary tallness. A distinctive feature of this disease is excessively long arms and legs.
2. . This disease develops after the closure of growth plates. Having stopped growing in length, human bones grow in width. In this case, soft tissue grows, which leads to a significant change in the appearance of a person. This especially applies to the skull, including the brow ridges, nose, ears and chin: they become wider. The same disease also develops in adults.

Treatment of gigantism in children and acromegaly is aimed at reducing the activity of growth hormone by administering injections of somastatin, a synthetic analogue of the hormone produced by the pituitary gland and blocking the activity of somatotropin.

Research conducted by scientists has shown that if IGF levels are often elevated, cancer cells may grow, leading to the development of lung and stomach cancer.

How is the level of FMI determined?

Determination of the concentration of protein secreted by the liver is required in order to assess dysfunction of the pituitary gland. And given that the production of growth hormone occurs very scatteredly and can fluctuate greatly, it is assessed on the basis of an analysis showing the concentration of IGF in the blood, since it remains practically unchanged throughout the day. Regardless of whether it is increased or decreased, the results will be reliable.

Features of the analysis

To obtain reliable results, it is necessary to take a blood test for the production of IGF if certain rules are observed.

1. The analysis is taken in the morning between 7 and 10 o'clock (otherwise the indicator may be slightly increased).
2. 8-12 hours before the test, you should not eat any food other than clean water.
3. Smoking and alcohol can distort test results. Therefore, they should also be abandoned.
4. Test results may be affected by medications. Therefore, you should stop taking them. The only exceptions are vital medications.
5. The day before the test, you should refrain from sports and any physical activity.
6. Half an hour before the start of the analysis should be spent in complete rest.

The level of IGF is influenced by the age and gender of the person donating blood.

The analysis is taken in several cases:

• for diseases caused by insufficient or excessive production of growth hormone;
• with gigantism or dwarfism in children;
• with acromegaly or an unknown reason for changes in appearance;
• if the bone age, determined on the basis of x-rays of the hands, does not correspond to the passport age;
• with existing disorders of the pituitary gland;
• to evaluate treatment with synthetic growth hormone.

What IFR norm is considered normal?

As mentioned above, the somatomedin level is influenced not only by concomitant diseases, but also by gender and age of the person. Therefore, it is very important that the level of FMI does not go beyond certain limits.

There are certain factors that can influence the test results. They can be increased by eating protein foods, physical activity and stressful situations, as well as taking testosterone.

Decreasing factors can be increased dosages of estrogen, pregnancy and obesity, inflammatory processes in the body and menopause.

Bibliography

1. Rosen V.B. Fundamentals of endocrinology.
2. Al-Shoumer K.A.S., Page B., Thomas E., Murphy M., Beshyah S.A., Johnston D.G. Effects of four years” treatment with biosynthetic human growth hormone (GH) on body composition in GH-deficient hypopituitary adults // Eur J Endocrinol 1996; 135:559-567.
3. Vorobyova O.A. Growth factors are new regulators of reproduction

Roman is a bodybuilding trainer with over 8 years of experience. He is also a nutritionist, and his clients include many famous athletes. The novel is with the author of the book “Sport and Nothing But..

Insulin-like growth factor 1 or somatomedin- necessary for the growth of a child; in adults it acts as an anabolic hormone.

Synonyms: insulin like growth factor-1, somatomedin C, IGF-1.

Insulin-like growth factor 1 is

a hormone similar in structure to insulin. Produced in the liver under the influence of growth hormone. At the same time it embodies the functions of the pituitary gland.

Synthesis stimulants

• HGH - growth hormone
• protein food

Unlike growth hormone, which enters the bloodstream in greater quantities at night, the concentration of IGF-1 is stable. It is released throughout life, and not only during periods of active growth.

Effects

• insulin-like growth factor - 1 - the main primary mediator of growth hormone in tissues; without it, growth hormone “does not work”
• stimulates the growth and development of cells, especially skeletal muscles, cartilage, bones, liver, kidneys, nerve fibers, stem cells, lungs
• slows down programmed cell death (apoptosis)
• activates the receptor (10 times weaker than insulin itself) - enters the cell, creates an energy reserve
• protects the heart from aging, increases “performance” and the ability of cardiomyocytes to divide

Symptoms of deficiency and excess of IGF-1 are the same as those of growth hormone.

Ongoing study of the role of IGF-1 in oncology. Several clinical trials have shown a greater likelihood of tumors in individuals with elevated somatomedin levels.

Deficiency Symptoms

• with a lack of insulin-like growth factor in children, short stature, slow physical and mental development, reduced muscle tone, doll-like face, lack of puberty
• in adults - decrease in muscle mass, changes in

Symptoms of excess IGF-1

• enlargement of the facial bones, especially the lower jaw and brow ridges
• enlargement of the hands and feet (gloves and shoes become small)
• increased sweating, fatigue, headache
• joint pain
• enlargement of internal organs (heart,)
• impairment of smell and vision
• decreased libido and erection (in men)
• impaired glucose tolerance and diabetes mellitus
• children are very tall

Features of the analysis

Donate blood for analysis for IGF-1 in the morning (7-10 hours), with the heart open, after 8-12 hours of fasting. You can drink non-carbonated water. Smoking and drinking alcohol is prohibited! If possible, stop taking medications (except vital ones). The day before and on the day of blood collection, it is prohibited to engage in physical exercise.

Hormone levels vary by age and gender.

The analysis does not replace the study of growth hormone!

Indications

• diseases and conditions with excess or deficiency of growth hormone
• short or very tall height in a child
• enlargement of individual body parts in an adult and changes in appearance
• discrepancy between official age and passport age
• assessment of pituitary function
• assessment of the success of treatment with growth hormone drugs

Norm, mg/l

• boys
  • 0-2 years - 31-160
  • 2-15 years - 165-616
  • 15-20 years - 472-706
• girls
  • 0-2 years - 11-206
  • 2-15 years - 286-660
  • 15-20 years - 398-709
• men and women
  • 20-30 years old - 232-385
  • 30-40 years old - 177-382
  • 40-50 years old - 124-310
  • 50-60 years old - 71-263
  • 60-70 years old - 94-269
  • 70-80 years old - 76-160

The level of insulin-like growth factor 1 in the blood is not determined by international standards, and therefore depends on the methodology and reagents used in the laboratory. In the laboratory test form, the norm is written in the column - reference values.

Additional Research

• - ( , ), ( , )
• glucose
• - TTG, St. T4

What influences the result of the analysis?

• increase IGF-1- protein foods, exercise, stress, dairy products, parenteral nutrition,
• reduce somatomedin- high doses of estrogens, xenobiotics, pregnancy (in the first trimester - below normal by 30%, in the second - by 20%, in the third - a gradual increase), obesity, menopause, inflammation

Reasons for the decline

• IGF-1 is reduced in pituitary growth hormone deficiency(pituitary dwarfism), with replacement growth hormone, IGF-1 levels return to normal
• Laron syndrome- insensitivity to growth hormone at the level of IGF-1, growth hormone in the blood is increased, and somatomedin is reduced
• mutation of GH receptors (SHP2 and STAT5B)
• anorexia nervosa and starvation
• protein deficiency in some extreme diets
• chronic liver and kidney diseases
• malabsorption - impaired absorption of nutrients in the intestine (for example, in chronic pancreatitis, after surgery to remove part of the intestine)
• decreased thyroid function (hypothyroidism)

Reasons for the increase

• acromegaly- tumor of the pituitary gland (less commonly of other organs), secreting growth hormone
• gigantism- increased secretion of growth hormone in childhood, before the closure of bone growth zones
• hyperpituitarism - increased function of the pituitary gland with the release of hormones

Data

• synthetic analogue of IGF-1(mecasermin), used to treat certain forms of dwarfism
• IFR-1 - indicator of the average level of STG
• consists of 70 amino acids in the form of a simple chain, molecular weight 7.649 Da.
• half-life of free IGF - 10 minutes, associated with receptors - 12-15 hours
• minimum levels of somatomedin in children under 5 years of age and the elderly

IGF-1 - insulin-like growth factor 1 was last modified: November 23rd, 2017 by Maria Bodyan