What glands are included in the endocrine system?

The endocrine system is composed of various glands responsible for producing and secreting hormones, which regulate numerous bodily functions including metabolism, growth, and mood. The pituitary gland, thyroid gland, and pancreas are key components of this system.

The pituitary gland, often referred to as the "master gland," controls many other hormone glands in the endocrine system. The thyroid gland regulates metabolism and energy use in the body. The pancreas functions as both an endocrine and exocrine gland; it releases insulin and glucagon to maintain blood sugar levels.

Other options included glands and organs that do not primarily function as part of the endocrine system. For instance, the liver, kidneys, heart, lungs, and digestive organs are involved in various physiological processes but are not classified as endocrine glands. Thus, option A accurately lists glands that are integral to the endocrine system.