Which hormone is a key regulator of metabolism?

Insulin is a key regulator of metabolism because it plays a crucial role in the way the body processes and utilizes glucose, the primary energy source for cells. When blood sugar levels rise after eating, insulin is secreted by the pancreas. This hormone facilitates the uptake of glucose into cells, promoting its use for energy or storage as glycogen in the liver and muscles. Additionally, insulin influences fat and protein metabolism, helping to regulate the synthesis and breakdown of fat and encouraging protein synthesis.

The other hormones listed do have important functions in the body, such as regulating reproductive processes or secondary sexual characteristics, but they do not primarily govern the metabolic processes in the same way that insulin does. Estrone and progesterone are more involved in reproductive health, while testosterone influences muscle mass and secondary sexual traits, rather than directly managing metabolic functions.