What are chemical substances secreted by endocrine glands called?

• A. Enzymes
• B. Minerals
• C. Neurotransmitters
• D. Hormones

Answer: (D)

Endocrine glands release chemical messengers called hormones into the bloodstream. Hormones travel to distant target organs and tissues, where they regulate processes such as metabolism, growth, and homeostasis. This distinguishes them from enzymes, which are catalysts for chemical reactions inside or outside cells and are not systemic signaling molecules secreted by endocrine glands. Minerals are inorganic nutrients, not signaling messengers. Neurotransmitters are chemical messengers released by neurons at synapses to affect nearby cells quickly, rather than circulating through the blood to distant targets.