You have 4 pea-sized glands behind the thyroid gland at the front of your neck. These glands are called parathyroids. They make a hormone called parathyroid hormone (PTH) that keeps the right levels of calcium in your blood and bones. PTH helps you absorb calcium from your food and keeps you from losing too much calcium in your urine. Sometimes, a growth on the parathyroid glands causes them to make too much PTH. This is called hyperparathyroidism (HPT).