Researchers found a simple new way to predict who might get kidney stones if they have an overactive parathyroid gland. By measuring calcium and magnesium in urine, doctors can identify patients at higher risk before stones develop. In this study of 109 patients, 40% had kidney stones. The new test, called CAMFE, was better at predicting stone risk than older methods. This discovery could help doctors catch the problem early and prevent painful kidney stones in people with parathyroid disease.

The Quick Take

  • What they studied: Can a simple urine test predict who will develop kidney stones when they have an overactive parathyroid gland?
  • Who participated: 109 patients diagnosed with primary hyperparathyroidism (overactive parathyroid gland). About 40% of them had kidney stones.
  • Key finding: A new measurement called CAMFE (calcium and magnesium in urine) successfully predicted kidney stone risk. Patients with lower CAMFE scores were more likely to have kidney stones. The test worked better than previous methods.
  • What it means for you: If you have an overactive parathyroid gland, this simple urine test might help your doctor predict your kidney stone risk early. However, more research is needed before this becomes standard medical practice.

The Research Details

Researchers looked back at medical records from 109 patients who had been diagnosed with primary hyperparathyroidism (an overactive parathyroid gland). They collected 24-hour urine samples from these patients while they ate a normal diet. They measured how much calcium and magnesium each person’s body was losing in their urine. Then they checked which patients had developed kidney stones and compared their urine measurements to those without stones.

The researchers used a mathematical method called logistic regression to find connections between the urine measurements and kidney stone formation. They also created a graph (ROC curve) to find the best cutoff number that would accurately identify who was at risk. This approach allowed them to test whether the new CAMFE measurement could reliably predict kidney stone problems.

Current methods for predicting kidney stones in parathyroid patients require collecting urine multiple times and running complicated tests. This new CAMFE measurement is simpler and faster. If it works as well as this study suggests, doctors could use it routinely to identify high-risk patients early, before painful kidney stones develop. Early identification means doctors can take preventive steps.

This study looked at real patient data, which is a strength. However, it was a retrospective study (looking backward at past records) rather than following patients forward over time. The sample size of 109 patients is moderate—larger studies would provide stronger evidence. The study was conducted at one institution, so results may need to be confirmed in different populations. The researchers did not mention adjusting for other factors that might affect kidney stone risk, such as diet or hydration levels.

What the Results Show

The CAMFE measurement showed a strong connection with kidney stone formation in patients with overactive parathyroid glands. The researchers found that patients with lower CAMFE values were significantly more likely to have kidney stones. The optimal cutoff value was 6.18—patients below this number had higher stone risk.

Patients who had formed kidney stones also had higher levels of calcitriol (an active form of vitamin D) in their blood. This suggests that their bodies were absorbing too much calcium from food, which then ended up in the urine and formed stones. The CAMFE measurement captured this problem in a simpler way than previous testing methods.

The test showed good predictive power, meaning it could accurately identify who was at risk. This was better than relying on single urine collections or other existing methods that required more complicated procedures.

The study confirmed that calcitriol levels were elevated in stone formers, supporting the theory that excessive calcium absorption drives stone formation. The researchers noted that CAMFE offers a practical advantage over dual urine collection protocols, which are time-consuming and inconvenient for patients. The single 24-hour urine collection needed for CAMFE is much easier for patients to complete.

Previous research has shown that kidney stones are common in people with overactive parathyroid glands, occurring in 15-20% of these patients. This study found 40% had stones, which is higher than expected. The CAMFE measurement builds on earlier research showing that calcium and magnesium excretion patterns matter. However, this is the first study to propose CAMFE specifically as a predictive tool. The simplicity of this approach is an improvement over existing methods that require multiple collections or complex calculations.

This study looked backward at existing patient records rather than following patients forward over time, which is less reliable for prediction. The study included only 109 patients from one medical center, so results may not apply to all populations. The researchers did not account for other important factors affecting kidney stone risk, such as how much water patients drank, their diet, or other medications they took. The study did not validate the CAMFE cutoff value in a separate group of patients, which would strengthen confidence in the 6.18 threshold. More research is needed before this test should be used routinely in clinical practice.

The Bottom Line

If you have been diagnosed with primary hyperparathyroidism, discuss with your doctor whether CAMFE testing might be appropriate for you. This is still a research finding and not yet standard practice. Current standard care includes monitoring calcium levels and kidney function. This test may become a useful addition to standard monitoring in the future. (Confidence level: Moderate—promising but needs more research)

This research is most relevant to people with primary hyperparathyroidism who want to know their kidney stone risk. It may also interest endocrinologists and nephrologists (kidney specialists) who treat these patients. People without parathyroid disease would not benefit from this test. Patients with secondary hyperparathyroidism (caused by kidney disease or vitamin D deficiency) may have different patterns and should not assume these results apply to them.

If this test becomes available, results would be available within days of providing a 24-hour urine sample. However, this is a risk assessment tool—it predicts future stone risk rather than treating existing stones. If your doctor identifies high risk, preventive measures (increased water intake, dietary changes, medication) might take weeks to months to show benefit in reducing stone formation.

Want to Apply This Research?

  • Track daily water intake (target: 2-3 liters) and urine output color (pale yellow indicates good hydration). Log any symptoms like flank pain or urinary changes. Record CAMFE test results and follow-up appointments with your endocrinologist.
  • Set daily hydration reminders to drink water consistently throughout the day. Use the app to log dietary calcium and sodium intake. Track any kidney stone symptoms and share this data with your healthcare provider at appointments.
  • Schedule quarterly check-ins to review CAMFE trends if the test becomes available. Monitor kidney function tests (creatinine, eGFR) annually. Track calcium levels from blood work. Use the app to maintain a symptom diary and share patterns with your doctor during regular visits.

This research describes a promising new test for predicting kidney stone risk in patients with primary hyperparathyroidism, but it is not yet standard medical practice. The CAMFE test should not be used to diagnose kidney stones or replace established diagnostic methods. If you have primary hyperparathyroidism or symptoms of kidney stones (severe back pain, blood in urine, painful urination), consult your doctor or endocrinologist immediately. Do not make changes to your treatment based on this research alone. Always discuss any new tests or treatments with your healthcare provider before proceeding.