Insulin-like growth factor is a hormone similar in its chemical structure to insulin. It regulates the processes of cell differentiation, their development and growth. Also involved in glucose metabolism.
Discovery history
Even in the late 50s of the twentieth century, scientists suggested that there is some kind of mediator between somatotropin (GH), which is also called growth hormone, and body cells. This conclusion suggested itself due to the fact that growth hormone had an effect only on a living organism, but when it was introduced into muscle cells, even if they were in a nutrient medium, no effect was observed.
In the 1970s, somatomedins were discovered, which were said mediators. They were called insulin-like growth factors. Initially, 3 groups of such substances were isolated: somatomedin A (IGF-3), B (IGF-2), C (IGF-1). But in the 1980s, it was determined that insulin-like growth factor 2, like 3, was only an experimental artifact, and in fact it does not exist. Only the presence of IGF-1 was confirmed.
Structure
Insulin-like growth factor 1(IGF-1) consists of 70 amino acids that form a chain with intramolecular bridges. It is a peptide that binds to plasma proteins, the so-called growth factor carriers. They allow somatomedin to maintain its activity much longer. It lasts several hours, while in free form the specified period is no more than 30 minutes.
The hormone is similar to proinsulin, for which it got its name. And insulin plays a huge role in the synthesis of somatomedin. After all, it helps the liver get all the necessary amino acids to start the mechanism for creating IGF.
Hormone Synthesis
This growth factor is considered an endocrine mediator that provides the action of somatotropic hormone. It is synthesized by liver hepatocytes as a response to receptor stimulation. In tissues, almost all the action of somatotropic hormone is provided by IGF-1. From the liver, it enters the bloodstream, and from there, through the mediation of carrier proteins, into tissues and organs. This hormone stimulates the growth of bones, connective tissue and muscles. Insulin-like growth factor is also synthesized independently in many tissues. If necessary, each cell can provide itself with this substance.
Secretion of IGF-1 by the liver is increased under the influence of estrogens, androgens, insulin. But glucocorticoids lower it. This is considered one of the reasons why these substances affect the growth and development of the body and the rate of its puberty.
Properties
IGF in muscle cells has growth-stimulating and insulin-like activity. It catalyzes protein synthesis and slows down the process of its destruction. It also shifts metabolism, promotes accelerated fat burning.
Insulin-like growth factor 1 is associated with the pituitary and hypothalamus. He his level in the blood depends on the release of other hormones. For example, at its low concentration, the secretion of somatotropin increases. It also increases the production of somatotropin-releasing hormone. But with a high level of IGF-1, the secretion of these hormones decreases.
There is a direct relationship between somatostatin and insulin-like growth factor. As one increases, so does the concentration of the other.
It is worth noting separately that athletes should not use it as an anabolic. The results of studies have been repeatedly published, which talk about the negative results of the experimental administration of drugs that contain insulin-like growth factor (IGF). Their intake can lead to diabetes, blurred vision, disruption of the heart muscle, neuropathy, hormonal disruptions. In addition, this substance is one of the main catalysts for the growth of cancerous tumors.
Features of an FMI
It has been observed that insulin-like growth factor 1 is lowered in old age and in childhood, and it is highest in adolescents. But researchers also found that older people who have a level of thishormone closer to the upper limit of the norm for their age group, live longer. In addition, they are less susceptible to diseases of the heart and blood vessels. Separately, it is worth noting that its amount increases during pregnancy.
The concentration in the blood during the day is approximately the same. Therefore, it is used to assess violations in the production of somatotropin. After all, the concentration of growth hormone in the blood changes throughout the day, the maximum level is determined at night. Therefore, it is problematic to accurately determine its amount.
Decreased hormone concentration
IGF-1 was only discovered in 1978. Since then, a lot of research has already been carried out, as a result of which a number of patterns have been established. So, its deficiency in childhood is the cause of growth retardation and physical development of the baby. But it is also dangerous if insulin-like growth factor is reduced in adults. Indeed, at the same time, underdevelopment of muscles, a decrease in bone density, and a change in the structure of fats are noted.
Caused by a lack of IGF can be a number of diseases. Among them are kidney and liver problems. Often the cause of a reduced amount of IGF is a disease such as hypopituitarism. This is a condition in which the production of hormones by the pituitary gland can completely stop or noticeably decrease. But the production of somatomedin also decreases with a nutritional deficiency, or, more simply, starvation.
FMI increase
Despite the dire consequences that a lack of IGF-1 causes, do not assume thatincreasing its quantity is not so scary.
So, if insulin-like growth factor 1 is elevated, it will lead to acromegaly in adults and gigantism in children. In children, the disease manifests itself as follows. They begin intensive growth of bones. This, as a result, causes not only huge growth, but also an increase in limbs to abnormally large sizes.
Acromegaly, which develops in adults, leads to the expansion of the bones of the legs, arms, face. The internal organs also suffer. This can be fatal due to cardiomyopathy - a disease in which the heart muscle is affected and its functions are impaired.
The most common cause of increased insulin-like growth factor is a pituitary tumor. It can be treated with medication, chemotherapy, or it can be removed surgically. The analysis helps to determine how successful the therapy is, or to check how well the operation was performed. For example, if the tumor was not completely removed, then the concentration of IGF will be increased.
Conducting research
To diagnose changes in the concentration of insulin-like growth factor in modern laboratory centers, the ICLA method is used. This is what is called immunochemiluminescent analysis. It is based on the immune response of antigens. At the stage of isolating the necessary substance, beacons are attached to it - phosphors, which are visible under ultraviolet light. The level of their glow is measured on special equipment - a luminometer. It determines the concentration of the isolated substance inserum.
Preparing for the study
In order to determine the insulin-like growth factor IGF-1, it is necessary to donate blood in the morning, always on an empty stomach. You are only allowed to drink plain water. The interval between the last meal and the sampling of material for research should be more than eight hours. It is important that the patient is at rest 30 minutes before the test. Venous blood is taken for research.
In addition, experts recommend refusing to conduct an analysis during acute respiratory diseases (viral or bacterial etiology) in order to exclude false results.
Average scores
When filling out the forms in the laboratory, it is important to enter the correct age. After all, it depends on him what the insulin-like growth factor should be. The norm is set for each age category individually. It is also necessary to focus not on average indicators, but on the data of the laboratory in which you took the tests. So, for example, in adolescents aged 14-16 years, the hormone level can be from 220 to 996 ng / ml. And in adults who are over 35 years old, it should not exceed 284 ng / ml. The older the patient, the lower the IGF limit should be. After 66 years, the norm is set within 75-212 ng / ml, after 80 - 66-166 ng / ml.
In children, the level of IGF will also depend on age. In newborn babies who are not yet 7 days old, it should be from 10 to 26 ng / ml. But after 16 days and up to 1 yearthe norm is set at 54-327 ng/ml.
Disease Diagnosis
By determining the insulin-like growth factor, a number of diseases can be diagnosed. An increase in its level indicates not only gigantism in children or acromegaly in adults. This may be a sign of tumors of the stomach and lungs, chronic renal failure. But it is worth noting separately that you can increase it by taking dexamethasone, alpha-agonists, beta-blockers.
Decrease in IGF levels in children may indicate dwarfism. In adults, levels are often lowered by hypothyroidism, cirrhosis of the liver, anorexia nervosa, or simply by starvation. Chronic sleep deprivation and the use of certain drugs with high doses of estrogen are other possible causes.
