What kind of substances do endocrine glands secrete?

Endocrine glands are specialized organs in the body that play a crucial role in regulating various physiological functions. They secrete hormones, which are chemical messengers that travel through the bloodstream to target organs and tissues, initiating specific biological responses. This process is essential for maintaining homeostasis, regulating metabolism, growth and development, and controlling mood and reproductive functions, among other things.

Hormones differ from neurotransmitters, which are released by neurons and act locally at synapses rather than entering the bloodstream. Similarly, enzymes, which are proteins that catalyze biochemical reactions in the body, have different functions and are not secreted by endocrine glands. Electrolytes, while important for numerous physiological processes, refer to ions in the body and are not secreted by endocrine glands in the same manner as hormones.

Therefore, the correct identification of hormones as the substances secreted by endocrine glands highlights their vital role in the endocrine system and the regulation of complex body functions.