Nothing wrong with your question dear. Nor with the answer moregoodtimes gave...........moving right along......
Grehlin is a peptide hormone, as you mentioned. So it circulates throughout the body (just like insulin - also a hormone). So Grehlin itself cannot be removed.
There is however an area of the stomach in the Greater Curvature (the fundus) where the P/D1 cells produce Grehlin. As this part of the stomach is removed in the vertical sleeve gastrectomy (VSG) procedure, there is a significant reduction in Grehlin production in the body (though it is still also produced in the epsilon cells of the pancreas). The less Grehlin in your system, the less hunger you feel.
The pharmacological mechanism is complex and I won't go into detail. However, it is important to note that Grehlin works in partnership with another hormone (Leptin) that induces satiation (a feeling of fullness and hunger satisfaction). Before you eat, increased Grehlin levels make you hungry and after you eat, increased Leptin levels let you know you're full (in addition to stomach stretch receptors).
In this equation, if you reduce the amount of Grehlin, but leave the amount of Leptin constant, your body will feel full faster (biochemically), in addition to the mechanical signal of fullness from the smaller stomach.
There is however no longer a stretch receptor area in the stomach (also removed in VSG procedure), and it takes time for the brain to register signals from stomach to tell it to stop eating. That is why VSG patients (especially in the beginning of solid food phase) can easily overeat. 1-2 additional bites past capacity happen frequently unless the patient is weighing their portions. The brain can't keep up with the mouth!
It is also important to note that Grehlin has other much more important and useful functions for the body! The ability to learn and adapt to change are influenced by Grehlin availability. It also has a role in glucose metabolism and cell transcription/migration. Some other studies point to Grehlin's role in protecting against stress-induced depression and sleep duration and quality.
So you don't want Grehlin removed completely!
Of course no amount of physical change to this complex interwoven system can fight the evils of head-hunger! That is a learned response that we must each battle through in the beginning and good routines, will-power and in many cases supportive psychotherapy are key to ongoing success!
