Leptin is a hormone that may bridge body composition and appetite. Body composition is determined by many factors. Genetics, or body type, the metabolic rate and the drive to eat are more innate factors. External factors include availability of food and activity level. However, there is an overlap of these factors. For example, activity level can change your drive to eat. A disorder of leptin is rare, but can be problematic.
Leptin
The appetite, or drive to eat, is coordinated by a part of the brain called the hypothalamus. Leptin is a protein hormone made by adipose, or fat tissues. The more fat tissues there are, the higher leptin levels get. Leptin signals the hypothalamus to decrease the appetite. It has other roles too, such as in proper development of the body.
Types
Leptin disorders have not been fully characterized, but there are two known basic mechanisms by which this disorder may manifest. The leptin gene is found on chromosome 7. Since there are two copies of each chromosome, there are two copies of leptin. If both of these copies are mutated, it can lead to a greatly increased appetite and obesity. If the leptin receptor is mutated, you may suffer from increased appetite and obesity as well. The second type is a resistance to the effects of leptin. When leptin is constantly high in the body, the cells of the hypothalamus can be desensitized to it. It is then less effective at decreasing your appetite.
Prevalence
The exact prevalence of significant leptin mutations leading to obesity is not known, but the majority of obese people do not have a leptin mutation. Other factors are contributing to the obesity. A 2005 review article in "Vitamins and Hormones" noted 16 known mutations in humans that may lead to obesity.
Treatment
In the rare forms of obesity linked to leptin mutations, administration of normal leptin may help to decrease the weight, along with other interventions. However, leptin given as a medication to obese people is not helpful. This is likely because they are desensitized to the effects of leptin. Obesity is linked to multiple health problems. Consult with a physician for the appropriate management and diagnosis.
References
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed 2008
- "Physiology"; Linda S.Costanzo; 4th Ed 2008
- "Vitamins and Hormones"; Leptin gene polymorphisms and their phenotypic associations.; van der Lende; 2005
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
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