Which of the following is a secretion produced by an endocrine gland?

• A. Saliva
• B. Sweat
• C. Bile
• D. A hormone

Answer: (D)

Endocrine glands release their products into the bloodstream as hormones, which act as chemical messengers to regulate distant tissues and organs. This distinguishes them from secretions that exit through ducts to surfaces or cavities. Saliva is produced by salivary glands and released into the mouth via ducts (exocrine). Sweat is secreted by sweat glands onto the skin surface (exocrine). Bile is produced by the liver and released into the digestive tract via bile ducts (exocrine). Because an endocrine gland’s secretion is a hormone, the hormone is the substance produced by an endocrine gland.