Most people have four parathyroid glands, located in the neck. Parathyroid glands secrete a substance creatively named parathyroid hormone a.k.a. PTH, which regulates levels of calcium in the blood. Sometimes, parathyroid glands can become big and overactive (hyperplastic) and secrete too much PTH; with all the extra PTH floating around your body, your calcium levels get too high. The classic symptoms of patients with elevated PTH and hypercalcemia are "stones (kidney stones), bones (fractures), moans (psychiatric problems) and groans (constipation - don't ask me, I didn't make this stuff up!)." One therapy for parathyroid hyperplasia is to surgically remove some or all of the glands. Exploratory neck surgery can be complicated; for example, there are important nerves in the neck that help control the vocal cords. For future ease of access for follow-up, after removing all four parathyroid glands, some surgeons will retransplant one gland back into the patient - sometimes in the patient's arm. It seems odd to take a gland from your neck and stick in a totally different part of the body, but the parathyroid gland doesn't mind and is perfectly happy to hang out by your elbow keep on secreting PTH into the blood.