Parathyroid hormone (PTH) is the most important regulator of calcium levels in the human body. When blood calcium becomes too low, calcium-sensing receptors in the parathyroid gland are activated and parathyroid hormone is secreted, thereby mobilizing calcium release from bone and suppressing calcium loss in urine. Measurement of PTH is important in determining the cause of excessively high or low calcium levels. High levels may be due to a parathyroid gland tumor, which is usually benign (primary hyperparathyroidism) or secondary hyperparathyroidism, which is usually a result of kidney failure. Low levels may be the result of a failure of the parathyroid gland. In primary hyperparathyroidism the parathyroid tumor must be removed.

 

PTH assays are used as a routine clinical tool to detect decreases in plasma PTH levels after all diseased tissue has been excised, even while surgery is taking place. The test allows a more limited procedure by confirming complete removal of diseased tissue and has reduced the need for repeated surgery. PTH assays in other conditions provide clinicians with important information that assists in managing patients with abnormal calcium levels.