What is a hallmark symptom of hypercalcemia?

Polyuria and polydipsia are hallmark symptoms of hypercalcemia primarily due to the effects of elevated calcium levels on renal function and overall fluid regulation. When serum calcium levels are high, the kidneys may become less efficient at concentrating urine, leading to increased urine output (polyuria). This results in accompanying thirst (polydipsia) as the body attempts to compensate for the fluid loss and prevent dehydration.

In hypercalcemia, the increased calcium influences the distal nephron, leading to the inability to concentrate urine properly. Additionally, high levels of calcium can also stimulate the thirst center in the hypothalamus, contributing to increased fluid intake. This combination of excessive urine production and increased thirst is quite characteristic of the condition, helping clinicians diagnose hypercalcemia during evaluation.

While other symptoms can occur with hypercalcemia, such as abdominal cramping due to muscle contractions or even neurological issues, polyuria and polydipsia specifically highlight the renal consequences of elevated calcium levels. This makes them central to diagnosing and understanding the metabolic implications of hypercalcemia.