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Growth hormone (GH)

Definition :-

– Growth hormone (GH) is a hormone that is essential for normal growth and development in children. It promotes proper linear bone growth from birth through puberty.

– In both children and adults, growth hormone helps regulate the rate at which the body both produces energy from food (metabolism) and makes lipids, proteins, and glucose (sugar).

– It also helps regulate the production of red blood cells and muscle mass.

– produced by the pituitary gland,. It is normally released into the bloodstream in pulses throughout the day and night with peaks that occur mostly during the night. Because of this, a single measurement of the level of GH in blood is difficult to interpret and not usually clinically useful. The value will be higher if the sample is taken during a pulse and lower if it is taken during a period between pulses. GH stimulation and suppression tests are therefore often used to diagnose GH abnormalities.

sample collected:

Because growth hormone is released in pulses, a single measurement of the blood level is not normally clinically useful. Therefore, testing for the suppression or stimulation of growth hormone release from the pituitary is usually done. After fasting for 10 to 12 hours, a blood sample is drawn from a vein in the arm.

– Sometimes, a single sample of blood is drawn following a fast and rest or after a period of strenuous exercise.

Clinical Significance :-

– GH stimulation tests help to diagnose GH deficiency and hypopituitarism. For a stimulation test, a sample of blood is drawn after 10-12 hours of fasting. Then, under close medical supervision, a person is given an intravenous solution of a substance that normally stimulates the release of GH from the pituitary. Blood samples are then drawn at timed intervals and GH levels are tested in each to see if the pituitary gland was stimulated to produce the expected levels of GH. The most commonly used stimulant is arginine, but others include clonidine and glucagon. Since exercise normally causes an increase in GH, vigorous exercise may also be used as the stimulant for GH release.

– GH suppression tests help to diagnose GH excess. For a suppression test, a sample of blood is drawn after 10-12 hours of fasting. A person is then given a standard glucose solution (usually 100 grams of glucose) to drink. Blood samples are drawn at timed intervals and tested for GH to see if the pituitary gland is sufficiently suppressed by the dose of glucose.

– Growth hormone stimulates the production of insulin-like growth factor-1 (IGF-1). IGF-1 is a hormone that mediates the effects of GH and helps promote normal bone and tissue growth and development. However, unlike GH, its level is stable in the blood throughout the day. This makes IGF-1 a useful indicator of average GH levels and the IGF-1 test is often used to help evaluate GH deficiency or GH excess.

– A GH suppression test and IGF-testing can also be used to monitor treatment of a GH-producing pituitary tumor. If a tumor is located, GH and IGF-1 levels can be measured after the tumor’s removal to determine whether the entire tumor was successfully removed. Tests may be ordered at regular intervals for years afterward to monitor GH production and to detect tumor recurrence.