page_title: Leptin
section_title: Effects
hierarchical_section_title: Leptin / Effects
caption_attribution_description: Two mice; the mouse on the left has more fat stores than the mouse on the right.
context_page_description: Leptin is a hormone predominantly made by adipose cells and enterocytes in the small intestine that helps to regulate energy balance by inhibiting hunger, which in turn diminishes fat storage in adipocytes. Leptin acts on cell receptors in the arcuate and ventromedial nuclei, as well as other parts of the hypothalamus and dopaminergic neurons of the ventral tegmental area, consequently mediating feeding.
  Although regulation of fat stores is deemed to be the primary function of leptin, it also plays a role in other physiological processes, as evidenced by its many sites of synthesis other than fat cells, and the many cell types beyond hypothalamic cells that have leptin receptors. Many of these additional functions are yet to be fully defined.
  In obesity, a decreased sensitivity to leptin occurs, resulting in an inability to detect satiety despite high energy stores and high levels of leptin.
context_section_description: Predominantly, the "energy expenditure hormone" leptin is made by adipose cells, and is thus labeled fat cell-specific. In the context of its effects, it is important to recognize that the short describing words direct, central, and primary are not used interchangeably. In regard to the hormone leptin, central vs peripheral refers to the hypothalamic portion of the brain vs non-hypothalamic location of action of leptin; direct vs indirect refers to whether there is no intermediary, or there is an intermediary in the mode of action of leptin; and primary vs secondary is an arbitrary description of a particular function of leptin.
  Location of action
  Leptin acts directly on leptin receptors in the cell membrane of different types of cells in the human body in particular, and in vertebrates in general. The leptin receptor is found on a wide range of cell types. It is a single-transmembrane-domain type I cytokine receptor, a special class of cytokine receptors. Further, leptin interacts with other hormones and energy regulators, indirectly mediating the effects of: insulin, glucagon, insulin-like growth factor, growth hormone, glucocorticoids, cytokines, and metabolites.
  Mode of action
  The central location of action (effect) of the fat cell-specific hormone leptin is the hypothalamus, a part of the brain, which is a part of the central nervous system. Non-hypothalamic targets of leptin are referred to as peripheral targets. There is a different relative importance of central and peripheral leptin interactions under different physiologic states, and variations between species.
  Function
  The primary function of the hormone leptin is the regulation of adipose tissue mass through central hypothalamus mediated effects on hunger, food energy use, physical exercise and energy balance. Outside the brain, in the periphery of the body, leptin's secondary functions are: modulation of energy expenditure, modulation between fetal and maternal metabolism, and that of a permissive factor in puberty, activator of immune cells, activator of beta islet cells, and growth factor.
caption: A comparison of a mouse unable to produce leptin, resulting in obesity, constant hunger, and lethargy (left), and an active normal weight mouse (right)
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