Which of the following metabolic abnormalities is typically seen in a patient with hyperparathyroidism?
Solution
Correct Answer: Option B
In patients with hyperparathyroidism, there is an excessive secretion of parathyroid hormone (PTH) by the parathyroid glands. PTH plays a critical role in regulating calcium and phosphate metabolism. Its primary effects include:
- Increasing calcium levels in the blood by stimulating osteoclast activity, which leads to bone resorption.
- Enhancing calcium reabsorption in the kidneys.
- Promoting the activation of vitamin D in the kidneys, which in turn increases intestinal absorption of calcium.
- Decreasing phosphate reabsorption in the renal tubules, resulting in increased phosphate excretion and thus hypophosphatemia, not hyperphosphatemia.
Therefore, the metabolic hallmark of hyperparathyroidism is hypercalcemia due to the above mechanisms.
- Option 1 (Hypocalcemia) is incorrect because PTH raises serum calcium.
- Option 3 (Hypokalemia) is unrelated to PTH activity.
- Option 4 (Hyperphosphatemia) is incorrect because PTH decreases serum phosphate levels.
In summary: In hyperparathyroidism, increased PTH secretion causes hypercalcemia and hypophosphatemia.
Reference: Harrison's Principles of Internal Medicine, 20th Edition, Volume 2, Chapter 342: Disorders of the Parathyroid Gland
- Increasing calcium levels in the blood by stimulating osteoclast activity, which leads to bone resorption.
- Enhancing calcium reabsorption in the kidneys.
- Promoting the activation of vitamin D in the kidneys, which in turn increases intestinal absorption of calcium.
- Decreasing phosphate reabsorption in the renal tubules, resulting in increased phosphate excretion and thus hypophosphatemia, not hyperphosphatemia.
Therefore, the metabolic hallmark of hyperparathyroidism is hypercalcemia due to the above mechanisms.
- Option 1 (Hypocalcemia) is incorrect because PTH raises serum calcium.
- Option 3 (Hypokalemia) is unrelated to PTH activity.
- Option 4 (Hyperphosphatemia) is incorrect because PTH decreases serum phosphate levels.
In summary: In hyperparathyroidism, increased PTH secretion causes hypercalcemia and hypophosphatemia.
Reference: Harrison's Principles of Internal Medicine, 20th Edition, Volume 2, Chapter 342: Disorders of the Parathyroid Gland
Practice More Questions on Our App!
Download our app for free and access thousands of MCQ questions with detailed solutions