Dynamics of Leptin and Endocrine Function

This is a study investigating the hormones and substances important to the stress response. The hormone that is most directly responsible for stress response is called corticotropin-releasing hormone (CRH). CRH is produced in the hypothalamus of the brain and causes the pituitary gland to produce another hormone called ACTH. The hormone ACTH then acts on the adrenal glands causing them to produce the hormone cortisol. Unfortunately, CRH levels are unable to be measured in simple blood samples. However, substances like cortisol and leptin can provide information as to the activity of the hypothalamus. The hormone leptin is associated with the regulation of body weight and the normal maintenance of bodily functions (homeostasis). It is found in fat cell (adipocyes) and communicates the nutritional status of the body to the brain (central nervous system). Research using animals has shown that defects in the communication between leptin and the brain causes obesity (the state of being overweight). It has also been noted that obese humans tend to have high levels of leptin. By studying patients with abnormal genes responsible for leptin production, researchers have found that a least one leptin gene must be intact for the normal secretion of hormones to proceed. These results show that the hormone leptin is produced outside of the brain in fat cells and acts directly on the function of the hypothalamus within the brain. Researchers believe that leptin plays a key role in the normal release of hormones from the HPA axis. Researchers intend on continuing to study the role of leptin in fat distribution, and the activity of the HPA axis in normal volunteers. In addition, this study will focus on the role of leptin in depression, because depression is characterized by changes in food intake, body weight, and neuroendocrine function. Data gathered from this study will provide a better understanding of the causes and medical consequences of major depression.