There are no other names used for the hormone but the gene, which encodes leptin, is known as the 'OB' gene.
Leptin, derived from the Greek word ‘leptos’, is a hormone released from fat cells otherwise known as adipocytes. Adipocytes are energy storing cells found in fatty tissue or adipose tissue. Leptin signals to the brain, in particular to an area called the hypothalamus. Leptin does not affect food intake from meal to meal but acts to alter food intake and control energy expenditure over a long period of time. Leptin has a more profound effect during weight loss. Weight loss leads to a reduction in adipose tissue and therefore levels of leptin fall. This leads to increased appetite to stimulate food intake. Therefore, leptin is a hormone that helps us maintain body weight in order to keep our body weight stable.
Because leptin is produced by fat cells, the amount of leptin released is directly related to the amount of body fat. This means the more fat an individual has, the higher the leptin levels are in their bloodstream. Therefore, leptin levels increase if an individual gains weight and, similarly, leptin levels decrease if an individual loses weight.
People with obesity have high levels of leptin. In some people with obesity, the brain does not respond well to leptin, so they have increased appetite despite adequate (or excessive) fat stores, a concept known as ‘leptin resistance’. This causes the fat cells to produce even more leptin. This is similar to the way people with type 2 diabetes have high levels of insulin, as their body is resistant to the effects of insulin. The cause of leptin resistance is still unclear.
There is an extremely rare genetic condition called congenital leptin deficiency, in which the body cannot produce leptin. In the UK, there are only about four families affected by this condition.
The absence of leptin makes the body think it does not have any fat stores and this results in uncontrolled food intake and severe obesity starting in childhood. In addition, leptin deficiency may cause delayed puberty and poor function of the immune system. This condition can be treated effectively with leptin injections, which result in significant weight loss, improvements in immune function and helps pubertal development to occur.
Last reviewed: Sep 2023
