What effect does increased PTH have on calcium and phosphate levels?

What effect does increased PTH have on calcium and phosphate levels?

• A. Increased calcium and increased phosphate
• B. Increased calcium and decreased phosphate
• C. Decreased calcium and increased phosphate
• D. No effect on calcium and phosphate levels

Answer: (B)

Increased levels of parathyroid hormone (PTH) have a significant impact on calcium and phosphate metabolism within the body. PTH is a critical hormone produced by the parathyroid glands that helps to regulate calcium levels in the blood.

When PTH is secreted in response to low calcium levels, it functions primarily by increasing the release of calcium from the bones into the bloodstream, leading to an increase in calcium levels. Simultaneously, PTH enhances renal tubular reabsorption of calcium, which also contributes to elevated serum calcium levels.

In terms of phosphate, PTH has a direct effect that decreases phosphate levels in the serum. It promotes phosphate excretion in the kidneys, leading to decreased phosphate reabsorption. As a result, even though calcium levels rise due to the actions of PTH, phosphate levels tend to decrease.

This combination of effects — increased calcium and decreased phosphate — is key in maintaining calcium homeostasis and is crucial for bone metabolism and health. Thus, the correct answer reflects the physiological actions of PTH on calcium and phosphate levels.