Clinical Chemistry And Pathologic Of Biochemistry (CCPB) Practice Test

Calcium homeostasis is controlled mainly by storage, absorption, and renal handling of calcium, coordinated by three key tissues: bone, intestine, and kidney. Bone acts as a reservoir that can release calcium into the bloodstream when needed, under hormonal control. The intestine is where dietary calcium is absorbed, a process driven by active vitamin D (calcitriol) to ensure enough calcium enters the body. The kidney regulates how much calcium is reabsorbed back into the bloodstream versus excreted in the urine, and it also activates vitamin D, further boosting intestinal calcium absorption. Because these three organs directly manage where calcium goes and how much stays in the blood, they are the primary players in maintaining calcium levels. The heart and lungs aren’t regulators of calcium balance, and while the liver contributes to vitamin D metabolism, the main direct effect on calcium homeostasis comes from bone, intestine, and kidney.