What is hyperparathyroidism? Hyperparathyroidism is the excessive production of parathyroid hormone by your parathyroid glands, which results in changes in your calcium and phosphorous levels. Parathyroid glands are located on or near the thyroid gland in your neck and are responsible for the regulation of calcium and phosphorous levels in your body. Despite the proximity of the thyroid and parathyroid glands, they serve distinct functions. Properly functioning parathyroid glands are required to sustain life. Fortunately, treatment is possible for overactive or underactive parathyroid glands. Overactive parathyroid glands (primary hyperparathyroidism) signal your body to increase the level of calcium in the blood by decreasing your excretion of calcium. More seriously, calcium may be harvested from the calcium in your bones. Mild hyperparathyroidism can often be treated simply by increasing your fluid intake, though more serious hyperparathyroidism may require surgical removal of one of the over-functioning parathyroid glands. High parathyroid levels are a normal body response to low blood calcium levels (known as secondary hyperparathyroidism). Renal (kidney) failure is the most common cause of secondary hyperparathyroidism. Your physician or health care professional can easily and quickly determine your levels of calcium, phosphorous, and parathyroid hormone with a simple blood test. These tests can also determine what type of hyperparathyroidism (primary or secondary) you may have. Seek prompt medical care if you are being treated for hyperparathyroidism but have mild symptoms that recur or are persistent. Seek immediate medical care (call 911) for serious symptoms, including coma; change in behavior, such as confusion, hallucinations or delirium; or severe abdominal pain, as these could be signs of a life-threatening condition.