Correct Answer: Spleen

Solution : The correct option is Spleen.

"Spleen" does not refer to an endocrine gland. Endocrine glands include the pituitary gland, thyroid gland, and adrenal glands, which produce hormones directly into the circulation to regulate numerous body activities. The spleen, on the other hand, is not essentially an endocrine gland; rather, its principal activities are connected to the immune system, and blood filtration rather than hormone release.