What elevated laboratory finding is indicative of hyperparathyroidism?

In hyperparathyroidism, one key laboratory finding is increased urinary calcium. This occurs because the overproduction of parathyroid hormone (PTH) leads to enhanced reabsorption of calcium from the bones and increased activity in the kidneys, which causes more calcium to be excreted in the urine. This is a hallmark of the condition, indicating that the parathyroid hormone is functioning abnormally and affecting calcium metabolism.

Increased urinary calcium is often used as a diagnostic marker to confirm hyperparathyroidism, especially in conjunction with elevated serum calcium levels. In contrast, the other test options do not reflect the metabolic changes associated with this condition. For example, decreased parathyroid hormone would not occur in hyperparathyroidism since the hallmark of the condition is high PTH levels. Similarly, elevated creatinine levels might indicate kidney function issues rather than a direct link to hyperparathyroidism, and elevated thyroid-stimulating hormone is unrelated to parathyroid hormone or calcium metabolism. Hence, increased urinary calcium serves as a primary indicator of hyperparathyroidism in the context of laboratory findings.