What organ system does adrenal glands belong? The adrenal glands belong to the endocrine organ system. This system is comprised of different glands in the body including (but not limited to) the thyroid gland, the parathy…roid glands, the adrenal glands, the pituitary gland, the gonads as well as the pancreas. The adrenal glands are located on top of each kidney, deep in the abdomen.