What is the main function of the endocrine system?

The main function of the endocrine system is to secrete hormones that regulate a wide variety of bodily functions, including growth, metabolism, and mood regulation. Hormones are chemical messengers that travel through the bloodstream to target organs and tissues, influencing physiological activities and maintaining homeostasis within the body.

This system includes glands such as the thyroid, adrenal glands, and pancreas, each of which produces specific hormones that play crucial roles in different bodily processes. For instance, insulin from the pancreas regulates blood sugar levels, while thyroid hormones regulate metabolism. The precise and coordinated release of hormones is vital for functions like reproduction, stress response, and energy management, highlighting the endocrine system's essential role in overall health and bodily function.

The other choices relate to different biological systems: fighting infections and regulating body temperature refers to the immune and thermoregulation systems; performing mechanical functions of movement pertains to the muscular and skeletal systems; and facilitating gas exchange in the lungs is the primary function of the respiratory system. Each of these systems has distinct roles that do not encompass the overarching purpose of the endocrine system.