Which hormone, when released into the bloodstream, signals the hypothalamus that the body has had enough food and reduces appetite while increasing fullness?

Which hormone, when released into the bloodstream, signals the hypothalamus that the body has had enough food and reduces appetite while increasing fullness?

• A. Leptin
• B. Ghrelin
• C. Insulin
• D. Leptin receptor

Answer: (A)

Leptin is the hormone that communicates energy stores to the brain. It’s released by fat cells in proportion to how much fat you have, so higher fat stores raise leptin levels in the bloodstream. When leptin reaches the hypothalamus, it binds to its receptors and nudges the brain toward fullness: it dampens the activity of hunger-promoting neurons and enhances signals that reduce appetite, signaling that the body has enough energy and should eat less. This makes leptin a key long-term regulator of energy balance and fullness. Ghrelin, by contrast, rises to stimulate appetite before meals. Insulin does influence appetite as well, but the classic signal of having enough energy stored that reduces hunger over time is leptin. The leptin receptor isn’t a hormone itself, so it doesn’t fit as the signaling molecule.

Leptin is the hormone that communicates energy stores to the brain. It’s released by fat cells in proportion to how much fat you have, so higher fat stores raise leptin levels in the bloodstream. When leptin reaches the hypothalamus, it binds to its receptors and nudges the brain toward fullness: it dampens the activity of hunger-promoting neurons and enhances signals that reduce appetite, signaling that the body has enough energy and should eat less. This makes leptin a key long-term regulator of energy balance and fullness.

Ghrelin, by contrast, rises to stimulate appetite before meals. Insulin does influence appetite as well, but the classic signal of having enough energy stored that reduces hunger over time is leptin. The leptin receptor isn’t a hormone itself, so it doesn’t fit as the signaling molecule.