The correct option is D All of the above
Endocrine glands are those glands which have no duct and release their secretions directly into the intercellular fluid or into the blood. The collection of endocrine glands makes up the endocrine system. The major endocrine glands found in the human system include the hypothalamus, pituitary gland, pineal gland, pancreas, ovaries, testes, thyroid glands and adrenal glands. Therefore, the correct answer is option D.