Which statement identifies parathyroid gland function?

• A. Decreases blood calcium level and increases phosphate
• B. Increases the blood calcium level and decreases the blood phosphate level
• C. Maintains constant blood calcium and phosphate
• D. Regulates thyroid hormones

Answer: (B)

The main concept is that parathyroid hormone raises blood calcium while lowering blood phosphate. When calcium levels drop, the parathyroid glands release PTH. It promotes calcium release from bone, increases kidney reabsorption of calcium, and stimulates activation of vitamin D, which boosts intestinal calcium absorption. At the same time, PTH reduces phosphate reabsorption in the kidneys, leading to more phosphate being excreted. The net effect is higher calcium and lower phosphate in the blood.

This is why the statement describing an increase in blood calcium and a decrease in blood phosphate best captures parathyroid function. The other options either describe opposite effects, suggest calcium/phosphate levels stay constant, or attribute thyroid hormone regulation to the parathyroids, which isn’t correct.