Orthopaedic Nurses Certification Board (ONCB) Metabolic/Inflammatory/Tumors Practice Exam

Which condition may lead to elevated serum phosphate levels in patients?

1. Hypoparathyroidism

2. Hyperparathyroidism

3. Osteoporosis

4. Paget's disease

The correct answer is: Hypoparathyroidism

Hypoparathyroidism is associated with elevated serum phosphate levels due to the underproduction of parathyroid hormone (PTH). In normal physiological conditions, PTH helps to regulate calcium levels in the blood and increases phosphate excretion through the kidneys. When there is insufficient PTH, as seen in hypoparathyroidism, phosphate excretion decreases, leading to an accumulation of phosphate in the serum. In contrast, hyperparathyroidism typically results in low serum phosphate levels because the excess PTH promotes renal phosphate excretion. Osteoporosis is primarily characterized by a decrease in bone density without necessarily affecting serum phosphate levels. Paget’s disease of bone primarily involves disorganized bone remodeling, which does not directly influence serum phosphate levels in the same way low PTH does. Overall, hypoparathyroidism directly causes an imbalance in phosphate metabolism, resulting in elevated serum phosphate levels.