During a critical period in infancy, influences the formation of neural circuits in the hypothalamus, which are responsible for determining the body's set point.

During a critical period in infancy, leptin influences the formation of neural circuits in the hypothalamus, which are responsible for determining the body's set point. The body's set point is the weight  range in which the body is programmed to function optimally. Leptin plays an important role in life, by altering the brain function that influences how much and individual or an animal later eats. 

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