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Causes of high and low calcium in urine
Last reviewed: 04.07.2025
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Hypercalciuria is the excretion of calcium in the urine in excess of 300 mg/day in men and more than 250 mg/day in women, or more precisely, the excretion of calcium in the urine in an amount greater than 4 mg/kg of ideal body weight per day in either sex.
Calcium stones account for 70-80% of all renal stones. Approximately 40-50% of patients with calcium stones have hypercalciuria. Forty percent of these patients have idiopathic hypercalciuria, 5% have primary hyperparathyroidism, and 3% have renal calcium acidosis. Other causes of hypercalciuria include excess vitamin D, calcium, and alkali intake, sarcoidosis, Cushing's syndrome, hyperthyroidism, Paget's disease, and immobilization.
Increased excretion of calcium in the urine is observed in hypercalcemia associated with malignant neoplasms, osteoporosis, dysfunction of the proximal tubules, and the use of diuretics (furosemide, ethacrynic acid).
The most common disorder in nephrolithiasis is idiopathic hypercalciuria. It is a heterogeneous disorder associated with increased urinary calcium excretion due to intestinal hyperabsorption (absorptive hypercalciuria) or decreased renal tubular calcium reabsorption (renal loss). Absorptive hypercalciuria may occur in a primary intestinal abnormality with hyperabsorption due to increased intestinal reactivity to calcitriol (type I) or increased serum calcitriol levels (type II). Increased calcitriol levels may cause renal phosphate loss, which will subsequently result in decreased serum inorganic phosphorus, increased calcitriol production, increased intestinal calcium absorption, increased serum calcium concentrations, and hypercalciuria (type III). Primary renal calcium loss impairs tubular reabsorption and may also cause hypercalciuria (renal hypercalciuria). Idiopathic hypercalciuria can be hereditary.
The serum inorganic phosphorus concentration is decreased in absorptive hypercalciuria type III due to the primary loss of phosphate through the kidneys. The PTH concentration increases in renal hypercalciuria because the primary disorder is a decrease in calcium reabsorption, which causes relative hypocalcemia and stimulates the release of PTH according to the principle of negative feedback. In absorptive hypercalciuria type II, the calcium content in the daily urine is normal, as in patients on a calcium-restricted diet (400 mg per day), because the absorption excess is not so significant. Nevertheless, the amount of calcium in the daily urine with calcium restriction in absorptive hypercalciuria types I and III, renal hypercalciuria remains high. Normal daily urinary calcium excretion with calcium restriction in food to 400 mg per day is less than 200 mg/day. The normal fasting urinary calcium concentration is less than 0.11 mg/100 ml SCF. The normal urinary calcium to creatinine ratio is less than 0.2 after taking 1 g of calcium as a load.
Determining the type of idiopathic hypercalciuria is important for selecting adequate drug therapy for kidney stone disease.
Hypocalciuria - a decrease in the concentration of calcium in the urine - occurs with nephritis, severe hypoparathyroidism, hypovitaminosis D, and hypothyroidism.
Urine calcium testing is essential for diagnosing familial hypercalcemia-hypocalciuria, in which urinary calcium excretion is less than 5 mmol/day in the presence of hypercalcemia.