Brain-Derived Neurotrophic Factor in Obesity and Brain Function

Study Summary

Background: \- Prader-Willi syndrome (PWS) and MC4R genetic mutations are two conditions that can cause problems with appetite regulation. People with PWS often have behavior and thinking problems. People with MC4R mutations may have problems with attention. These problems may be related to Brain-Derived Neurotrophic Factor (BDNF), a protein that is important for brain development. Researchers want to study people with PWS and MC4R mutations to see how BDNF is involved in these conditions. Specifically, body weight and brain function will be studied, and compared with healthy volunteers. Objectives: \- To study how BDNF affects body weight and brain function in people with PWS and MC4R mutations. Eligibility: * Individuals of any age who have Prader-Willi syndrome or MC4R genetic mutations. * Healthy volunteers of any age to act as control participants. Design: * Participants will be screened with a medical history and physical exam. Height, weight, and waist/hip circumferences will be measured. Blood samples will be taken for genetic and other tests. * Participants will fill out questionnaires about eating habits, pain perception, and sleep behavior. * Participants will keep a 3-day food diary to record all food and drinks eaten. * Tests and questionnaires will be given to study thinking, speech, movement, behavior, and mood. Some tests will be done on a computer; other tests will be on paper. Tests may also involve performing tasks with blocks and other objects. * Participants may have other tests as directed. These will include hot and cold sensitivity tests, imaging studies like x-rays, and measurements of body fat and water content. * Treatment will not be provided as part of this study.