Hyperparathyroidism

Parathyroid hormone (PTH) is released when the body senses too little circulating calcium. It raises serum calcium by increasing calcium release from bone, increasing renal calcium reabsorption, promoting phosphate excretion, and stimulating vitamin D activation so the intestine absorbs more calcium. In primary hyperparathyroidism, one or more parathyroid glands secrete PTH autonomously. The critical pattern is hypercalcemia with an elevated or inappropriately normal PTH. A normal PTH is not reassuring when calcium is high; normal parathyroid glands should suppress PTH production in response to hypercalcemia. The excess calcium affects excitable tissues, the kidneys, the gastrointestinal tract, and bone. It can slow neuromuscular activity, impair concentration, reduce bowel motility, promote dehydration, and increase filtered calcium in the urine. Persistent PTH excess also draws calcium from bone, increasing fracture risk. Do not treat all elevated PTH concentrations as primary disease: - Primary hyperparathyroidism: calcium is high and PTH is not suppressed. - Secondary hyperparathyroidism: PTH rises appropriately in response to chronic hypocalcemia or a low-normal calcium level, commonly with chronic kidney disease or vitamin D deficiency. - Tertiary hyperparathyroidism: prolonged secondary stimulation,...