The primary organs involved in the maintenance of calcium homeostasis are the intestine, _____, and kidney.

The primary organs involved in the maintenance of calcium homeostasis are the intestine, _____, and kidney.

• A. Bone
• B. Liver
• C. Skin
• D. Pancreas

Answer: (A)

Calcium balance is achieved through coordinated actions in intestine, bone, and kidney. The blank is bone because bone serves as the major calcium reservoir that can release calcium into the bloodstream when needed, via remodeling driven by parathyroid hormone. When calcium is low, PTH stimulates bone resorption, increases renal calcium reabsorption, and promotes activation of vitamin D, which in turn boosts intestinal calcium absorption. Calcitonin helps lower calcium by inhibiting bone resorption, but it’s not the primary regulator. Liver and skin participate in vitamin D metabolism, but they aren’t the main regulatory organs like bone, intestine, and kidney; the pancreas has no direct role in calcium homeostasis.

Calcium balance is achieved through coordinated actions in intestine, bone, and kidney. The blank is bone because bone serves as the major calcium reservoir that can release calcium into the bloodstream when needed, via remodeling driven by parathyroid hormone. When calcium is low, PTH stimulates bone resorption, increases renal calcium reabsorption, and promotes activation of vitamin D, which in turn boosts intestinal calcium absorption. Calcitonin helps lower calcium by inhibiting bone resorption, but it’s not the primary regulator. Liver and skin participate in vitamin D metabolism, but they aren’t the main regulatory organs like bone, intestine, and kidney; the pancreas has no direct role in calcium homeostasis.