Final answer:
Leptin is a hormone produced by adipose tissue that helps regulate hunger and maintain energy balance. It is also necessary for proper reproductive functions. In obesity, leptin resistance can lead to overeating and weight gain.
Step-by-step explanation:
The hormone leptin is secreted by adipose tissues in the hypodermis in response to food intake. Its primary function is to regulate energy balance by inhibiting hunger, which in turn diminishes the desire to eat and promotes a feeling of satiety. Leptin plays a significant role in appetite control by increasing the activity of anorexigenic neurons and decreasing that of orexigenic neurons.
Moreover, leptin is crucial for proper reproductive function. It is essential for the production of GnRH (gonadotropin-releasing hormone) and gonadotropins. When body fat and, consequently, leptin levels are too low, this can result in delayed puberty in females and reduced fertility. However, as adipose levels increase, so does leptin production, which can improve fertility.
In the context of obesity, leptin resistance is a condition where despite high levels of fat reserves, the body's sensitivity to leptin decreases, leading to an impaired sense of satiety and a tendency to overeat.