Parathyroid hormone (PTH) is a single-chain polypeptide hormone secreted by the parathyroid glands. PTH helps the body maintain stable levels of calcium in the blood. It is part of a feedback loop that includes calcium, PTH, vitamin D, and, to some extent, phosphorous (phosphate) and magnesium. Conditions and diseases that disrupt this feedback loop can cause inappropriate elevations or decreases in calcium and PTH levels and lead to symptoms of hypercalcemia or hypocalcemia. EXCESSIVE secretion of parathyroid hormone is seen in two forms: · Primary hyperparathyroidism is the result of parathyroid gland disease, most commonly due to a parathyroid tumor (adenoma) which secretes the hormone without proper regulation. Common manifestations of this disorder are chronic elevations of blood calcium concentration (hypercalcemia), kidney stones and decalcification of bone. · Secondary hyperparathyroidism is the situation where disease outside of the parathyroid gland leads to excessive secretion of parathyroid hormone. A common cause of this disorder is kidney disease - if the kidneys are unable to reabsorb calcium, blood calcium levels will fall, stimulating continual secretion of parathyroid hormone to maintain normal calcium levels in blood. Secondary hyperparathyroidism can also result from inadequate nutrition - for example, diets that are deficient in calcium or vitamin D, or which contain excessive phosphorus (e.g. all meat diets for carnivores). A prominent effect of secondary hyperparathyroidism is decalcification of bone, leading to pathologic fractures or "rubber bones". INADEQUATE production of parathyroid hormone - hypoparathyroidism - typically results in decreased concentrations of calcium and increased concentrations of phosphorus in blood. Common causes of this disorder include surgical removal of the parathyroid glands and disease processes that lead to destruction of parathyroid glands. The resulting hypocalcemia often leads to tetany and convulsions, and can be acutely life-threatening. Other related tests: Calcium, Phosphorus, Vitamin D.
EDTA whole blood sample. • Whole blood sample collected in an EDTA tube must be stored on ice during transportation. • Plasma must be separated within 30-60 minutes from the time of blood withdrawal. • Early morning sample is preferable, but NOT compulsory • No fasting needed