Somatomedin-C (insulin-like growth factor – I/IGF-I)
Why this test?
To find out the growth abnormalities causes.
To evaluate the pituitary gland functioning.
In order to control the effectiveness of excess or deficiency treatment of GH. The best indicator of the effectiveness of growth hormone treatment for children suffering from growth hormone deficiency is their grow’s rate.
Immunity to GR information. If IGF is normal, GH deficiency is excluded.
To help in the diagnosis of hypopituitarism (along with tests for other pituitary hormones such as adrenocorticotropic hormone).
To detect a pituitary tumor that produces GH. In particular, in case of surgery to find out whether the entire tumor was successfully removed and tracking possible recurrences years after.
In what cases is it prescribed?
If children have symptoms of GH deficiency, such as slow growth.
When adults have symptoms of GH deficiency: reduced bone density, rapid fatigue, adverse changes in lipid composition, low endurance during exercise (however, IGF testing is not standard for patients with these symptoms because GH and IGF deficiency are rarely the cause of these disorders).
If hypophysis is suspected.
When monitoring the effectiveness of growth hormone treatment (rare).
With symptoms of gigantism in children or acromegaly in adults (along with a test for GH suppression).
After surgery to remove the GH-producing tumor (to confirm that it has been completely removed).
When drug or radiation therapy undergoing, which is usually carried out after surgery to remove a tumor.
After the tumor removing surgery, in order to control the production of GH and detect a possible recurrence in time.
The result of the insulin-like growth factor (IGF) test is an indirect indicator of the amount of growth hormone (GH) produced by the body. IGF and GR are polypeptide hormones, small protein molecules that are necessary for normal growth and development of bones and body tissues.
GH is produced by the pituitary gland, a small gland located at the base of the brain at the level of the bridge of the nose. It is secreted into the bloodstream in waves throughout the day, reaching its maximum level, as a rule, at night. IGF is synthesized by the liver and skeletal muscles, as well as many other tissues, in response to their stimulation by growth hormone. IGF is important for many functions of growth hormone, stimulates the growth of bones and other tissues of the body, and also contributes to an increase in muscle mass. It reflects the excess and deficiency of growth hormone.
The concentration of IGF, like the concentration of GH, is very low in early childhood, then it increases, reaching a peak during puberty, and decreases with the adults.
Deficiency of IGF and GH can be caused, for example, by hypopituitarism or a tumor of the pituitary gland, which, damaging the cells that produce the hormone, prevents its synthesis. Lack of IGF is also observed in the absence of sensitivity to GR, which can be caused by malnutrition, hypothyroidism, lack of sex hormones and some chronic diseases. Genetic insensitivity to GR (GR resistance) is very rare. GR deficiency in early childhood can interfere with a child's growth and development. In adults, hormone deficiency can lead to a decrease in the density of bone tissue, underdevelopment of muscles and changes in the composition of lipids. However, GH or IGF testing is usually not prescribed to adults with reduced bone density, muscle atrophy, or lipid deficiency - only in very rare cases is GH deficiency and, as a result, IGF deficiency the cause of these disorders.
An excess of GH and IGF can contribute to the abnormal formation of the skeleton, as well as other manifestations of gigantism and acromegaly. With gigantism, excessive growth of bones occurs in children, which is the reason for very high growth, as well as an increase in arms and legs to abnormally large sizes. In case of adults, acromegaly causes thickening of the bones and soft tissues, such as nasal tissue growth. As a result, the consequence of an excess of GH can be an increase in internal organs, such as the heart, as well as type 2 diabetes, cardiovascular diseases, in particular hypertension, arthritis and a decrease in life expectancy. The most common cause of increased growth hormone secretion is a pituitary tumor (usually benign). It can usually be removed surgically or treated with drugs or chemotherapy. In most cases, this leads to the normalization of GH and IGF.