From the Guidelines
Urinary calcium is primarily caused by the body's calcium metabolism and excretion processes, and the main causes of elevated urinary calcium (hypercalciuria) include excessive dietary calcium intake, increased intestinal absorption of calcium, decreased renal calcium reabsorption, and increased bone resorption. The causes of elevated urinary calcium can be multifactorial, including medical conditions such as hyperparathyroidism, vitamin D excess, certain medications (like loop diuretics, corticosteroids), renal tubular acidosis, sarcoidosis, and some cancers 1. Genetic factors also play a role, as idiopathic hypercalciuria often has a hereditary component. Prolonged immobilization can increase bone breakdown, releasing more calcium into the bloodstream and subsequently into urine. High sodium intake can increase urinary calcium excretion as well, as sodium and calcium share reabsorption pathways in the kidneys.
Some key factors that can influence urinary calcium levels include:
- Dietary calcium intake: High dietary calcium intake can increase urinary calcium excretion, but it can also help bind dietary oxalate in the gut, reducing oxalate absorption and urinary excretion 1
- Sodium intake: High sodium intake can increase urinary calcium excretion, and reducing sodium intake to less than 2.4 g/day can help decrease urinary calcium levels 1
- Potassium intake: Higher potassium intake is inversely associated with incident kidney stones in men and older women, and potassium citrate can help prevent calcium precipitation in the urine 1
- Vitamin D intake: Vitamin D excess can lead to increased urinary calcium excretion, and calcium supplements may increase the risk of stone formation, especially if taken in between meals 1
Elevated urinary calcium is clinically significant because it can lead to kidney stone formation, particularly calcium oxalate or calcium phosphate stones, and in severe cases may contribute to bone demineralization and osteoporosis. To manage urinary calcium levels, clinicians may recommend dietary changes, such as limiting sodium intake and consuming 1,000-1,200 mg per day of dietary calcium, as well as increasing fluid intake to achieve a urine volume of at least 2.5 liters daily 1. Thiazide diuretics may also be prescribed to patients with high or relatively high urine calcium and recurrent calcium stones, as they can help reduce urinary calcium excretion 1.
From the Research
Urinary Calcium Causes
- The provided studies do not directly address the causes of urinary calcium, but rather focus on the treatment of hyperparathyroidism and its effects on calcium levels 2, 3, 4, 5, 6.
- However, it can be inferred that hyperparathyroidism, which is characterized by elevated parathyroid hormone (PTH) levels, can lead to increased calcium levels in the blood and potentially in the urine 4, 5.
- Cinacalcet, a medication used to treat hyperparathyroidism, has been shown to decrease PTH levels and normalize serum calcium levels, but its effect on urinary calcium is not explicitly stated in the studies 2, 3, 4, 5.
- One study found that cinacalcet did not significantly affect urinary calcium levels in patients with primary hyperparathyroidism 5.
Hyperparathyroidism Treatment
- Parathyroidectomy (surgical removal of the parathyroid glands) and cinacalcet are two treatment options for hyperparathyroidism, with varying degrees of success and side effects 2, 3, 4, 6.
- Studies have shown that parathyroidectomy can be an effective treatment for hyperparathyroidism, particularly in patients with severe disease or those who do not respond to medical therapy 2, 4, 6.
- Cinacalcet, on the other hand, has been shown to be a safe and effective treatment for hyperparathyroidism, with benefits including decreased PTH and serum calcium levels, but may not be as effective as parathyroidectomy in correcting metabolic disorders 3, 4, 5.