Leptin

Leptin is a hormone produced mainly by fat cells that signals the brain about stored energy. It helps regulate appetite, energy expenditure, and body weight.

Leptin receptor: A cell-surface receptor that binds leptin and activates intracellular signaling pathways. Receptors in the hypothalamus translate leptin signals into changes in appetite and energy balance.
Adipokine: A signaling molecule secreted by adipose tissue that affects processes elsewhere in the body. Leptin is one of the hormones through which fat tissue communicates with other organs.
Congenital leptin deficiency: A rare inherited condition in which absent or severely reduced leptin causes early-onset hyperphagia and obesity. This condition demonstrates how loss of leptin signaling can profoundly disrupt appetite regulation.
Ob gene: The mouse gene whose mutations cause severe obesity and whose product was identified as leptin. Identifying the gene led researchers to the hormone it encodes.
Leptin resistance: Reduced physiological responsiveness to leptin despite normal or elevated circulating hormone levels. It helps explain why high leptin in common obesity does not reliably suppress appetite.
Hypothalamus: A brain region that coordinates functions including hunger, temperature, and hormone regulation. Leptin acts on hypothalamic circuits that adjust feeding and energy expenditure.
Energy homeostasis: The regulation of energy intake, storage, and expenditure to maintain physiological balance. Leptin contributes to this balancing system by conveying information about energy reserves.
Leptin replacement therapy: Treatment that supplies leptin to people with leptin deficiency or certain disorders of fat metabolism. Replacement can correct the specific hormone deficit in congenital leptin deficiency.
Jeffrey M. Friedman: An American molecular geneticist whose laboratory identified leptin in 1994. His team isolated leptin by studying the mouse obesity gene.
Blood–brain barrier: A selective interface that regulates movement of substances between blood and the central nervous system. How leptin reaches relevant brain circuits may constrain signaling in obesity.

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