On the back side of the thyroid gland, which is located along the front of your windpipe, there are four small glands known as parathyroid glands. These small glands are responsible for regulating your calcium levels, and too little or too much of this mineral can be detrimental to your health. When these glands produce too much parathyroid hormone, hyperparathyroidism occurs. This condition causes high levels of calcium to leach from your bones and build up in your bloodstream, and this puts you at an increased risk of developing osteoporosis, high blood pressure, heart disease and kidney stones.