Remember, hypER-parathyroidism is MUCH more common than hypOparathyroidism. Hypoparathyroidism is the state of decreased secretion or decreased activity of parathyroid hormone (PTH). This lack of PTH leads to decreased blood levels of calcium (hypocalcemia) and increased levels of blood phosphorus (hyperphosphatemia). There are no symptoms of too little parathyroid hormone other than the symptoms due to having a blood calcium that is too low.