I. Secretion and regulation of growth hormone
Characteristics: Pulsatile secretion, age-related, with the largest pulse amplitude and the most secretion in the middle of puberty.
Frequency: about 3-5 hours apart, about 8 pulses/day.
Peak: Secretion peaks one hour after sleep, and the amount of secretion is more than half of the total amount of the day.
Regulation: The hypothalamus secretes two neurohormones.
1. growth hormone-releasing hormone (GHRH).
2. growth hormone releasing inhibitory hormone (SRIH).
The central nervous system regulates the secretion of GHRH and SRIH through neurotransmitters such as dopamine, 5-hydroxytryptamine and norepinephrine.
Second, growth hormone excitation test results determine.
1.Growth hormone is secreted in the body at a peak, and the usual value is very low (0-5ng/ml are normal), only 3-5 peaks appear at night during deep sleep (the child may wake up during night blood collection, and the number of blood collection needs to be more for a long time, so it is not used).
2.The peak level cannot be detected by random blood collection, unlike thyroid hormone and other hormones whose concentration is usually constant in the blood, which can be checked by blood collection at any time.
3. Only the usual value cannot reflect whether the growth hormone is normal or not.
Method of growth hormone stimulation test.
1. The test is performed in the early morning without exercise and on an empty stomach. Start fasting and water the night before the test, at least 8 hours fasting for children >2 years old and 6 hours fasting for infants <2 years old. Fasting during the whole test.
2. In accordance with the treatment standard for growth hormone deficiency, the growth hormone stimulation test of two drugs must be done separately (to avoid a 15% false positive rate for one drug in the stimulation test).
3, stimulation test drugs: combined drugs (insulin, colistin, arginine, levodopa and other drugs selected from two).
4, stimulate the test route of administration: oral and intravenous; use oral and intravenous two kinds of medication, respectively, can reduce the possibility of rapid effect of oral drugs due to digestion and absorption.
5.The time and number of blood collection for the stimulation test: Blood is collected once before the drug is administered to determine the basic growth hormone value; blood is collected 30, 60, 90 and 120 minutes after the drug is administered to measure the growth hormone level.
6.Judgment of growth hormone stimulation test results.
(1) GH peak value ≥10ng/ml at any one time is normal.
(2) GH peak <5ng/ml is complete lack.
(3) 5ng/ml < peak GH < 10ng/ml for partial deficiency.
GH excitation test is the main means to diagnose growth hormone deficiency dwarfism (GHD).
IV. Analysis of the problems arising from the stimulation test.
1.Why did the child get dizzy during the stimulation test?
A: Because colistin has a hypotensive effect, many children feel dizzy, which is a normal phenomenon, rest and lie down can be relieved.
2.Will too much blood be taken to harm the child’s body?
A: In fact, there is no need to worry, the total amount of blood collected does not exceed 15ml, the human spleen is used to destroy mature red blood cells, about 30ml per day, after we draw blood, the spleen will compensate for the destruction of some.