Hormones as chemical messengers regulated by the liver

Steps:

• Identify the key traits: produced by the body, alters target organ activity, destroyed by the liver.
• Recall that hormones are chemicals secreted by endocrine glands to influence distant organs.
• Note hormones travel via bloodstream and are inactivated by liver metabolism.
• Match to options: only hormones fit all criteria.

Why C is correct:

• Hormones are defined as signaling molecules produced by glands that regulate target organ functions and are degraded by the liver to prevent overactivity.

Why the others are wrong:

• A. Bile aids digestion in the intestines but is produced by the liver, not destroyed by it.
• B. Enzymes catalyze reactions locally and are not typically transported to alter distant organs or destroyed by the liver.
• D. Saliva lubricates the mouth for digestion and is produced by salivary glands, not affecting target organs systemically or degraded by the liver.

Final answer: C