What is the primary function of parathyroid hormone (PTH) in calcium homeostasis, and where does it act in the kidney to influence phosphate?

What is the primary function of parathyroid hormone (PTH) in calcium homeostasis, and where does it act in the kidney to influence phosphate?

• A. Raises serum calcium by stimulating bone resorption, increases renal calcium reabsorption in the distal tubule, and decreases proximal tubular phosphate reabsorption.
• B. Lowers serum calcium by inhibiting bone resorption and reducing renal calcium reabsorption.
• C. Increases phosphate reabsorption in the proximal tubule, raising serum phosphate.
• D. Suppresses calcitriol production and has no effect on renal calcium.

Answer: (A)