Idiopathic Hypercalciuria and Osteoporosis

What is Idiopathic Hypercalciuria?

Despite the intimidating name, idiopathic hypercalciuria is really a simple concept—it is when you release too much calcium in your urine. We don’t entirely know the cause, but it appears to be related to a complex interaction between your genetics, diet, and environment. Those with idiopathic hypercalciuria may pull calcium from their bones to make up for the calcium lost in their urine, leading to bone loss and an increased risk for osteoporosis-related fractures.

How is Hypercalciuria Diagnosed?

Those with idiopathic hypercalciuria do not necessarily experience any symptoms to indicate they have the disease. When symptoms are present, the most common include frequent urination, abdominal pain, and recurrent kidney stones.

To diagnose idiopathic hypercalciuria, we first have to eliminate other possible causes of excessive calcium in the urine, including kidney disease and hyperparathyroidism. Once these have been ruled out, we use the 24 hour urine calcium test to diagnose hypercalciuria.

• 24 Hour Urine Calcium. This lab measures the amount of calcium released in your urine over a 24 hour period of time. The test confirms hypercalciuria if women release more than 250 mg/day, or men release more than 300 mg/day. A weight-based formula also exists, which can establish the diagnosis if urinary calcium levels are greater than 4 mg/kg/day.

How Does Hypercalciuria Impact Your Bones?

Idiopathic hypercalciuria receives relatively little attention when it comes to possible causes of osteoporosis. However, studies have shown that the condition is present in approximately 10% of postmenopausal women with osteoporosis, and nearly 20% of men and premenopausal women with osteoporosis! Perhaps it’s time that we start taking this disease a little more seriously when it comes to your bone health.

The jury is still out on exactly how hypercalciuria leads to osteoporosis. Studies looking to solve this dilemma have come to conflicting conclusions.

• Using a microscope to look at bone changes, researchers concluded that the primary finding was decreased formation of new bone. Bone breakdown appeared normal, or only slightly increased.
• When evaluating blood tests, researchers found evidence of both increased bone breakdown and increased new bone formation, which doesn’t seem to match the microscope analysis.

Regardless of the exact mechanism, it is clear that those with idiopathic hypercalciuria have a bone density 10-15% less than people without the condition!

How Can Those With Hypercalciuria Improve Their Bone Health?

Hypercalciuria can be treated using a class of medications known as thiazide diuretics. These medications decrease the amount of calcium released in your urine, and have been shown to improve bone density and decrease your risk of fractures. If your fracture risk remains high despite thiazides, then traditional osteoporosis medications can be used to lower this risk.