These four small glands are not so well known as the thyroid gland, yet they are also vital for perfect health of the body. They are oval-shaped masses of cells, each weighing about thirty milligrams. They are located outside the thyroid gland and have an independent blood supply. They secrete a hormone called para-thyroxin (also called parathormone) which controls the calcium level in the blood. In this manner these tiny glands influence the growth and regeneration of the bones in the body. If they function incorrectly, then the bones can either become too soft or too brittle, either of which can have disastrous effects. Sarvangasana improves the efficiency and health of these glands in the same way as was explained for the thyroid gland.