Leptin
Leptin is a hormone made largely by fat cells that helps signal your brain about energy stores and appetite. Its level tends to track with how much body fat you carry.
Leptin plays a role in the long-term regulation of hunger, fullness, and energy balance. Studying it can offer insight into how your body's appetite-signaling system is behaving. Because it interacts with metabolism and weight, it is sometimes explored as part of a broader metabolic evaluation.
A higher leptin often accompanies higher body fat, and in some cases the brain may respond less strongly to it, a pattern sometimes called leptin resistance. Levels also vary with sleep, timing of meals, and sex. Your clinician interprets it alongside your overall health picture.
A lower leptin generally accompanies lower body fat stores. In rare cases, unusually low levels relate to specific hormonal or genetic conditions that a clinician would evaluate.
There is no single ideal leptin target, and reference ranges vary by lab and body composition. Your clinician can help interpret your result in context.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.