Which glands are listed as endocrine structures?

• A. Adrenal glands, ovaries, pancreas, parathyroid glands, pineal, pituitary, testes, thymus, thyroid
• B. Heart, Lungs, Stomach
• C. Kidneys, Liver, Spleen
• D. Spinal cord, Brain, Nerves

Answer: (A)

Endocrine glands are organs that release hormones directly into the bloodstream to regulate activities throughout the body. The list that includes adrenal glands, ovaries, pancreas, parathyroid glands, pineal, pituitary, testes, thymus, and thyroid contains the classic hormones-secreting glands. Adrenal glands produce cortisol and adrenaline; ovaries and testes secrete sex hormones; the pancreas has an endocrine portion that makes insulin and glucagon; parathyroid glands regulate calcium with PTH; the pineal gland makes melatonin; the pituitary acts as a master gland with hormones that control other glands; the thymus secretes thymosin involved in immune function; and the thyroid releases thyroxine and calcitonin. Pancreas is noted for having both endocrine and exocrine roles, which is a helpful nuance in understanding how some organs participate in multiple systems. The other options describe organs whose primary roles are not hormone-secreting glands—the heart, lungs, and stomach are involved in circulation, respiration, and digestion, respectively; the kidneys, liver, and spleen have important hormonal functions but aren’t classified primarily as endocrine glands; and the spinal cord, brain, and nerves belong to the nervous system.