Pentagastrin is a polypeptide which does not occur naturally in the body and is procured synthetically. This polypeptide can have various effects on the body, especially when given parenterally. The polypeptide may cause gastrin in the body. Pentagastrin is responsible for the secretion of gastric acids, intrinsic factor and pepsin. The polypeptide has especially been useful in a diagnostic technique for testing calcitonin.
Calcitonin is a polypeptide amino acid hormone. In humans, calcitonin is specifically secreted by parafollicular cells which are present in the thyroid. The hormone helps to reduce calcium ions which may be present in the blood. It has an opposing effect on the parathyroid hormone, which acts to increase the concentration of calcium radicals in the blood stream. Calcitonin has no special functions in terms of regulation of calcium or its breakdown in the body.
Pentagastrin binds itself to a receptor for the cholecystokinin-B. This receptor is largely expressed in the brain. When the receptor is activated, it in turns activates another receptor known as the phospholipase C. This is a second messenger which can cause panic attacks. Usually, if pentagastrin is given intravenously, it may cause panic attacks.
For diagnosis purposes, pentagastrin stimulation is used to elevate the levels of serotonin artificially. When the serotonin is elevated, the body shows symptoms of carcinoid syndrome. When the serotonin levels are thus elevated, the body experiences flushing. This diagnostic technique is specifically used for those who do describe flushing as a symptom but have normal or slightly elevated levels of biochemical markers for the syndrome. This test is known as the pentagastrin stimulation test.
Pentagastrin is also used in the stimulation of the gastric mucosa. This is done in nuclear medicine in order to detect Meckels diverticulum.
The Pentagastrin stimulation test is a very popular test and has become the most widely used and accepted stimulation test for CT secretion. For the test to be performed the patient is made to fast overnight and the CT in the basal serum is tested in the morning. Pentagastrin is then slowly injected intravenously. The quantity of pentagastrin to be injected is usually determined by the doctor. However, the patient is usually given 0.5 µg of pentagastrin per kilogram of body weight. After the injection has been administered, the serum CT is checked again after about 3-5 minutes.
Though there are other stimulation tests for measuring serum CT, they have lower sensitivity and therefore, are not recommended by many doctors.