What is a major function of the adrenal gland?

The major function of the adrenal gland is the regulation of metabolism, which encompasses a variety of processes that manage how the body converts food into energy, responds to stress, and maintains overall homeostasis. The adrenal glands, located on top of each kidney, produce hormones such as cortisol, which plays a significant role in glucose metabolism and the body’s response to stress. Other hormones produced by the adrenal glands, including adrenaline and norepinephrine, are crucial for the 'fight or flight' response, further supporting metabolic functions during stressful situations.

The other options are associated with different bodily systems and organs. The production of insulin is primarily the function of the pancreas, which regulates blood sugar levels. Filtration of blood is mainly performed by the kidneys, which remove waste products and excess substances from the bloodstream. The transport of oxygen is the main role of red blood cells in the circulatory system, facilitated by the protein hemoglobin. Each of these processes is essential for health, but they are not performed by the adrenal glands.