Insulin Resistance in Hypercalciuric Calcium Kidney Stone Patients.

RATIONAL & OBJECTIVE: Diabetes and uric acid kidney stones are strongly associated. Patients with calcium kidney stones also have higher risk of developing diabetes compared with nonkidney stone patients yet this has not been further investigated. We aimed to characterize insulin resistance in calcium kidney stone patients.

STUDY DESIGN

Observational.

SETTING & POPULATION: This study was performed in the University of Chicago Clinical Research Center. Kidney stone patients (N = 42) were selected for having idiopathic hypercalciuria and calcium stones with no other medical conditions, and controls (N = 27) were healthy.

EXPOSURES

All participants presented to the Clinical Research Center in a fasting state and at least 2 timed fasting blood and urine collections were collected before a fixed breakfast. Six additional timed blood and urine collections were performed after breakfast.

OUTCOMES

We compared fasting and fed indices of insulin resistance between the groups.

ANALYTIC APPROACH

We used tests and multivariable linear regression models. A sensitivity analysis removing all patients who had ever been on a thiazide diuretic was also performed.

RESULTS

In separate multivariable linear models, kidney stone patients had higher fasting serum insulin levels (24 (3-46 pmol/L),  = 0.03) and higher homeostatic model of insulin resistance (HOMA-IR) (1.0 (0.2-1.8),  = 0.02). In separate multivariable linear models, kidney stone patients had higher fed serum glucose levels (10 (2-18 mg/dL),  = 0.01). Results were similar in a sensitivity analysis removing all patients who had ever been on a thiazide diuretic. There were no differences in urine composition based on HOMA-IR levels.

LIMITATIONS

Single institution. Small sample size limited subanalyses by different calcium stone types.

CONCLUSIONS

Calcium kidney stone patients without diabetes or other medical conditions demonstrated signs of insulin resistance compared with healthy matched controls.