In simple terms, when your body produces growth hormone another hormone called Somatostatin is also produced in proportion to the amount of growth hormone produced or injected. As the level of GH production rises so does that of Somatostatin. At a level called the Threshold, Somatostatin will inhibit the pituitary from producing more GH. As the GH levels decrease so does the level of Somatostatin. At some point the inhibitory (negative feed back) effect of Somatostatin on the production of GH is lost and GH production can start back up.
When a person is using injectable GH, it doesn't matter that Somatostatin goes up shutting off the natural production of GH because, you are replacing the lost production with the injectable GH. In fact, studies have found after just 48 hours of GH injections your natural production of GH has drops by 40% and after 30 days your natural production of GH is at zero. This is caused by the high and sustained production of Somatostatin when rhGH is used.
Documentation of patients using GH, the GH levels have been recorded to elevate above the baseline. When this spike in GH occurs and is at or above the Threshold, Somatostatin shuts off the natural GH production by the pituitary gland. Therefore, patients using GH can experience a drop-off in GH production which is corrected by lowering the dose of GH. Somatostatin is suppressed even further by the use of more arginine.
Additionally, when a patient who is using injectable GH stops, it can take up to a year for their own pituitary function to reestablish full production.
Laboratory and GH
The time that it takes for any medication, introduced into the body, to reduce by half the amount is called the Half-Life.
The Half-life of Growth Hormone is 20 minutes, IGF-1 is 8 minutes, and IGF Binding Protein-3 is 20-24 hours. So when performing morning blood work the most stable and consistent of the growth hormone markers to test for is IGFBP-3; not IGF-1!! Performing both IGF-1 and IGFBP-3 testing gives the most accurate information for growth hormone.
It is Growth Hormones direct affect upon the liver that IGF-I, IGF-II, IGFBP-1 to IGFBP-6, and ALS are manufactured. A subset of this information is that any of these is not produced there is a genetic or physiological issue with the liver. ( an up coming lecture on "The Influence of Growth Hormone on the Liver".
Before starting any hormonal supplementation either prescriptive or not take the appropriate blood tests to make sure that you need it and how much. Avoid the Blind-Leading-The-Blind mentality, it can be expensive and also hurt you.