Hypoparathyroidism is a combination of symptoms that occur due to inadequate parathyroid hormone (PTH) production. It is very rare and most commonly occurs because of damage to or removal of parathyroid glands during parathyroid or thyroid surgery. Less commonly, it can be caused by a defect present at birth (congenital) in which a person is born without parathyroid glands. Decreased secretion or activity of parathyroid hormone leads to decreased blood levels of calcium (hypocalcemia) and increased levels of blood phosphorus (hyperphosphatemia).