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Leptin

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Formal name: Leptin
Related tests: Lipid Profile, Thyroid Panel, Glucose, A1c, Insulin, Ghrelin

The Test Sample

What is being tested?

Leptin is an adipokine, a hormone produced primarily by fat cells (adipocytes) and to a lesser degree by other tissues, including the placenta in pregnant women. This test measures the amount of leptin in the blood.

Leptin is a hormone that helps regulate appetite by signaling hunger satisfaction (satiety) to receptors in the hypothalamus in the brain; when sufficient food has been consumed, it tells the body that it is no longer hungry. In a normal feedback response, a low level of leptin triggers hunger and an increase in food consumption. As the level of leptin rises from an increase in fat cells, hunger diminishes and food consumption drops off.

Insufficient leptin can cause persistent hunger as the body attempts to protect itself from perceived underfeeding (starvation). Very rare inherited leptin deficiencies can cause severe obesity through constant hunger and constant eating that starts in early childhood. Leptin replacement therapy has been shown to be successful in treating some of those affected.

Obesity is most commonly associated with elevated leptin levels. This is thought to be due to a resistance to leptin that is similar to the insulin resistance often seen with obesity. People who are affected are resistant to the action of leptin—they continue to experience hunger even after consuming sufficient food. The body continues to produce more leptin in an attempt to compensate and in response to the perceived hunger. However, about 10% of those who are obese are estimated to have some degree of leptin deficiency.

There is significant interest in better understanding leptin's ties to obesity. Obesity is a major health concern in the U.S. because it increases the risk of many conditions, such as high blood pressure (hypertension), dyslipidemias (high cholesterol and/or high triglycerides), type 2 diabetes, joint problems, sleep apnea, coronary heart disease, stroke, and some cancers. The rate of obesity has increased steadily over the last 20 years in all age ranges and, according to the Centers for Disease Control and Prevention, more than one-third of adults and 17% of children and teens in this country are currently classified as obese. Classification is based on body mass index or BMI. (See Common Questions #2).

A recent study found that in some people a leptin level might be more accurate than the traditional body mass index in gauging how much excess fat a person is carrying. In general, the higher the level of leptin in the bloodstream, the more fat tissue a person has. In the study, this was especially true with older women and in those with large muscles or dense bones where the results of the BMI score could be misleading.

Research is ongoing to evaluate leptin's roles in the body and the links between leptin and obesity, and between leptin and successful weight loss. There is also continued interest in determining whether a leptin-based treatment might be useful for those who are obese and leptin-deficient.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.