Glucagon-like peptide-1, or GLP-1, is a hormone produced naturally by specialized cells lining the intestines. As part of the body’s metabolic system, its release is a direct response to eating. This process connects digestion to the body’s broader energy regulation.
The Natural Function of GLP-1
When you eat, GLP-1 is released into the bloodstream within 10 to 15 minutes. One of its primary roles is to interact with the pancreas, where it stimulates the release of insulin when blood sugar levels are elevated. This glucose-dependent action helps cells absorb sugar from the blood for energy.
Simultaneously, GLP-1 suppresses the pancreas from releasing another hormone called glucagon. Glucagon signals the liver to release stored sugar into the blood. By inhibiting glucagon, GLP-1 helps prevent blood sugar levels from rising too high after a meal.
Another function of GLP-1 is to slow gastric emptying, the rate at which food moves from the stomach into the small intestine. This moderates nutrient absorption, preventing sharp blood sugar spikes, and contributes to a feeling of fullness.
Finally, GLP-1 communicates with appetite centers in the brain’s hypothalamus. It sends signals of satiety, or fullness, which helps regulate food consumption and control appetite.
Pharmacological GLP-1 Activation
The natural GLP-1 hormone is very short-acting, lasting only a few minutes before being broken down by an enzyme called dipeptidyl peptidase-4 (DPP-4). For a more sustained medical effect, a class of drugs called GLP-1 receptor agonists was developed. These medications mimic the natural hormone but are engineered to resist degradation.
Synthetic versions, such as semaglutide and liraglutide, are known as agonists because they bind to and activate the same GLP-1 receptors. By activating these receptors in the pancreas and brain, the drugs replicate GLP-1’s natural effects for a much longer duration—often for many hours or even a full week.
This extended duration allows for a continuous therapeutic effect. Instead of the brief signal from the body’s own GLP-1, receptor agonists provide a constant signal. This sustained activation leads to more pronounced effects on blood sugar control, appetite, and gastric emptying.
GLP-1 receptor agonists are administered as injections under the skin in fatty tissue, such as the abdomen or thigh. Oral formulations are also available. A healthcare provider determines the dosage and frequency based on the specific medication and the patient’s needs.
Therapeutic Outcomes of Activation
The primary medical applications for GLP-1 receptor agonists are managing type 2 diabetes and chronic weight management. For individuals with type 2 diabetes, these medications improve glycemic control through their effects on insulin and glucagon. This leads to lower blood sugar levels after meals and can significantly reduce HbA1c, a marker of long-term glucose control.
For weight management, the therapeutic effects are driven by the agonists’ action on the brain and stomach. By slowing gastric emptying and signaling satiety, these medications can lead to a reduced desire to eat. This reduction in calorie intake often results in significant weight loss for individuals with obesity or who are overweight.
Beyond glucose control and weight loss, some GLP-1 receptor agonists reduce cardiovascular risk. Clinical trials show that certain drugs in this class can lower the risk of events like heart attack and stroke in patients with type 2 diabetes. These benefits appear related to effects on blood pressure, lipid levels, and inflammation, independent of weight loss.
Common Side Effects and Medical Considerations
The most common side effects of GLP-1 receptor agonists are gastrointestinal. Patients may experience nausea, vomiting, diarrhea, and constipation, especially when first starting the medication or after a dose increase. These symptoms are mild to moderate and tend to decrease as the body adjusts.
Less frequent but more serious risks require medical attention, including pancreatitis and gallbladder problems, such as gallstones. This class of drugs has an FDA boxed warning for a potential risk of thyroid C-cell tumors, based on animal studies. For this reason, they are not recommended for patients with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.
These medications are available by prescription only and require supervision by a healthcare professional. A provider will assess an individual’s health status and medical history to determine if the drug is appropriate. They will also monitor for side effects and effectiveness, making adjustments as needed.