Hypocalciuria in overt and subclinical celiac disease.

OBJECTIVE: To investigate indices of calcium (Ca) homeostasis in celiac disease (CD). METHODS: Urinary Ca excretion rate, intestinal absorption of strontium (Sr) (used as index of intestinal Ca absorption), and other variables related to these end points were measured in newly diagnosed, untreated adult patients (n = 32) with overt and subclinical CD and compared with those of healthy controls (n = 27). Subclinical CD was defined by the absence of diarrhea (> or = 3 bowel movements/24 h), steatorrhea (fecal fat excretion > 6 g/24 h), and low body mass index (weight/height, kg/m2 < 21). RESULTS: Compared with controls, untreated celiac patients had 2 x lower Ca excretion (p < 0.0001) in 24-h and overnight urine (fed condition) but normal Ca excretion in urine samples collected under fasting (2-h) condition; the increase in urinary Ca excretion from fast to fed condition was 4 x lower in untreated celiac patients (p < 0.0001). Patients with overt and subclinical CD did not have significantly different urinary Ca excretion rates. Sr absorption rate was 45% lower in untreated patients than controls (p < 0.0001). Patients with overt and subclinical CD did not have significantly different Sr absorption rates. Sr absorption rate (r = 0.576, p < 0.0001) related to the increase in urinary Ca excretion from fast to fed condition. In celiac patients, 24-h urinary Ca excretion increased by 52% (p < 0.0001) over baseline after 6 months of gluten-free diet, and urinary Ca excretion under fasting condition did not significantly change. CONCLUSIONS: Overt and subclinical CD is associated with low urinary Ca excretion under fed condition, which relates to low intestinal absorption.