What is the most common cause of hypercalcemia in the normal population?

Primary hyperparathyroidism is the most common cause of hypercalcemia in the normal population due to its prevalence and the underlying mechanisms involved. In this condition, there is an overproduction of parathyroid hormone (PTH) from the parathyroid glands, leading to increased calcium release from bones, enhanced renal tubular reabsorption of calcium, and increased intestinal absorption of calcium via activation of vitamin D. This hormone dysregulation results in elevated serum calcium levels.

Primary hyperparathyroidism often presents in asymptomatic individuals who may be identified during routine biochemical screening. The condition can be caused by a benign adenoma of the parathyroid glands, hyperplasia, or, less commonly, malignancy. The connection between this disorder and hypercalcemia makes it essential to recognize, especially since it is relatively common compared to other causes of elevated calcium levels.

While malignancy can also lead to hypercalcemia through various mechanisms, including osteolytic metastases and paraneoplastic syndromes, it is more commonly observed in specific populations or with advanced disease. Calcium deficiency and overdose pertain to different physiological processes and are less frequent causes of hypercalcemia in a healthy population.