Somatotropic hormone (STH)

Why this test? 

Analysis of somatotropic hormone is not recommended for a general examination of the body. In general, testing is carried out only in case of suspicion of disorders related to its secretion, and is prescribed after performing tests on other hormones or to help in researching the function of the pituitary gland.

The analysis is performed to check the excess or insufficient amount of production of somatotropic hormone and to obtain information about how severe the disease is. It is part of a diagnostic examination to find out the causes of abnormal synthesis of somatotropic hormone, and in addition, it can be used to evaluate the effectiveness of treatment for acromegaly or gigantism.

In what cases is it prescribed? 

The somatotropic hormone stimulation test is performed if the child has the following symptoms of this hormone deficiency: 

• growth retardation in early childhood - at the same time, the child is much lower than his peers; 
• diagnosis of the thyroid gland (for example, the determination of free T4) indicates the absence of hypothyroidism (since insufficient work of the thyroid gland can also slow down growth); 
• X-ray examination shows delayed bone growth; 
• here is a suspicion that the pituitary gland has reduced activity. 

A stimulation test in adult patients may be necessary for symptoms of somatotropic hormone deficiency or hypopituitarism: reduced bone density, fatigue, lipid metabolism disorders, reduced resistance to physical exercise.

As a rule, tests for other hormones are performed first to see if other diseases are the cause of these symptoms. Insufficiency of the synthesis of somatotropic hormone is a rather rare phenomenon both among children and among adults. Hormone deficiency in adults can occur due to a genetic predisposition to hypothalamic or pituitary disease. 

A test for inhibition of somatotropic hormone secretion is performed if a child shows signs of gigantism or an adult shows signs of acromegaly. Such an analysis may also be necessary in the case when a pituitary tumor is suspected, sometimes the test is performed together with an analysis for insulin-like factor - 1 and analyzes for other hormones to monitor the effectiveness of the treatment of the disease. Tests for somatotropic hormone and insulin-like factor-1 can be performed regularly at certain intervals over many years to monitor possible r

Test information 

Along with the analysis for somatotropic hormone, an analysis for insulin-like factor is often performed. The latter also reflects an excess or a lack of somatotropic hormone, but its level remains stable throughout the day, thereby making it an indicator of the average content of somatotropic hormone. Diagnosis of STH abnormalities often includes a test for its stimulation and suppression, which are used to assess the function of the pituitary gland and changes in the level of somatotropic hormone. 

The stimulation test helps to diagnose the lack of somatotropic hormone and hypopituitarism. For this, blood is taken from the patient's vein after 10-12 hours of abstinence from food, then insulin or arginine solution is administered intravenously under medical supervision. 

Further, blood samples are taken at certain intervals, each of which determines the content of somatotropic hormone to find out whether insulin (or arginine) affects the pituitary gland, producing the expected level of the hormone. In addition, clonidine and glucagon are used to stimulate somatotropic hormone. The suppression test helps to diagnose excess hormone, and together with other blood tests and scintigraphy - to identify and localize pituitary tumors. 

To carry out this test, blood is taken after 10-12 hours of abstinence from food. Then the patient swallows a standard glucose solution, after which, at certain time intervals, blood tests are performed, in which the content of somatotropic hormone is determined, to check whether the pituitary gland is sufficiently suppressed by the dose of glucose taken. 

To check the functioning of the pituitary gland, other tests are often used, such as an analysis of T4 (thyroxine), thyroid-stimulating hormone, cortisol, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (in men). They are usually performed before an analysis for somatotropic hormone in order to make sure that their indicators correspond to the norm or are under the control of the drugs taken. For example, hypothyroidism in children must be treated before testing for somatotropic hormone deficiency, otherwise the results may be falsely low. 

The blood sample taken for the test for suppression of the level of somatotropic hormone is also used for the analysis of the glucose level to make sure that the patient's body is sufficiently suppressed by the glucose solution taken. 

Since physical exercise usually temporarily increases the level of somatotropin hormone, sometimes its insufficiency is assessed after intensive exercise performed over a period of time. Tests for growth hormone and insulin-like growth factor may be periodically prescribed for children who have undergone radioactive treatment of the central nervous system or radiation before stem cell transplantation. 

This is a fairly common treatment for acute lymphoblastic leukemia, where radiation can affect the hypothalamus and pituitary gland and thus affect growth;

The analysis determines the amount of somatotropic hormone in the blood. 

Somatotropic hormone is produced by the pituitary gland, a gland the size of a grape, located at the base of the brain behind the bridge of the nose. The hormone is usually secreted into the blood in waves during the day with a peak concentration, usually at night. 

Somatotropic hormone is necessary for the normal growth and development of children, as it helps to increase the length of the bones from the very birth of the child until the end of puberty. If there is a lack of growth hormone, the child grows more slowly. 

Excessive production of somatotropin hormone is often observed with a tumor of the pituitary gland (usually benign). Excessive synthesis of the hormone contributes to excessive bone elongation and continued growth even after puberty, which can lead to gigantism (height above 2 meters).

Also, with an excess of somatotropic hormone, coarse facial features, general weakness, delayed sexual development and headaches can be observed. Although growth hormone partially loses its activity in adults, it continues to play a role in the regulation of bone density, maintenance of muscle mass, and fatty acid metabolism: hormone deficiency can lead to decreased bone density, decreased muscle mass, and changes in lipid levels. 

However, the analysis for somatotropic hormone is not a common practice for examining patients with reduced bone density, underdeveloped muscles, and with increased lipid content - a lack of somatotropic hormone is rarely the cause of these disorders.

Excessive production of somatotropic hormone in adults can cause acromegaly, the characteristic feature of which is not bone elongation, but their excessive thickness. Although symptoms such as thickening of the skin, sweating, fatigue, headache and joint pain are not severe at the onset of the disease, further increases in hormone levels can lead to enlargement of the hands and feet, carpal tunnel syndrome (painful feeling in the wrist) and pathological enlargement of internal organs. 

Papillomas on the body and polyps in the groin sometimes appear due to the increased level of somatotropic hormone.