Parathyroid Glands

About the Parathyroid Glands

The parathyroid glands are four small glands approximately 5 mm each, located on the posterior surface of the thyroid gland. They produce parathyroid hormone PTH, the master regulator of blood calcium. PTH increases blood calcium by stimulating osteoclasts bone resorption, increasing intestinal calcium absorption via activated vitamin D, and increasing renal calcium reabsorption while increasing phosphate excretion. PTH also stimulates 1 alpha hydroxylase in the kidney, converting 25 OH D to active 1,25 di OH D. Calcium sensing receptors on parathyroid cells regulate PTH secretion. Primary hyperparathyroidism, most often caused by a single benign adenoma and less often by hyperplasia of all four glands, causes hypercalcemia stones, bones, groans, psychic moans. Hypoparathyroidism from accidental removal during thyroid surgery causes hypocalcemia tetany, perioral numbness, Chvostek and Trousseau signs. Management of hypoparathyroidism typically involves calcium and active vitamin D. The parathyroid glands were among the last major organs to be described, identified in humans by the Swedish medical student Ivar Sandstrom in 1880.