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OneLiner

Parathyroid adenoma causes an increased PTH level. The increased PTH results in hypercalcemia, which causes his variety of symptoms (kidney stones, pain in the bones, abdominal groans, and psychiatric overtones). The parathyroid glands secrete PTH, which helps regulate how the body uses calcium. PTH protects the serum ionized calcium concentration by increasing calcium levels and decreasing phosphate levels. PTH primarily acts on the bones, the gut, and the kidneys. It stimulates osteoclast activity and thus, bone resorption, releasing both calcium and phosphate. In the gut, PTH indirectly stimulates calcium absorption by the intestine by stimulating 1α-hydroxylase to produce 1,25-dihydroxyvitamin D (1,25-OH, the active form of vitamin D, also known as calcitriol). PTH acts on the kidneys by decreasing phosphate reabsorption (and therefore, increasing phosphate excretion). Overall, the net effect of PTH is increased free calcium and decreased phosphate, as calcium is increased via bone resorption and gut absorption, and phosphate is decreased through kidney excretion.