The present study investigated whether overnight urine collection can replace 24-hour urine collection to measure urinary calcium (Ca) excretion in healthy individuals. One hundred healthy men (age 25-74 years) on their usual diet participated in the present study as part of an ongoing epidemiological population-based survey. Two separate bags (daytime and overnight bags) were given together with instructions to collect a complete 24-hour urine sample divided in to the daytime and the overnight specimen. Urinary Ca was analyzed by atomic absorption spectrophotometry and creatinine by the picric acid colorimetric method. Overnight urinary Ca was correlated to daytime (r = 0.618, p < 0.0001) and 24-hour urinary Ca (r = 0.891, p < 0.0001). In the 17 men found to have hypercalciuria (24-hour urinary Ca > or = 7.5 mmol), the overnight urinary Ca averaged 4.44 +/- 0.29 mmol/12 h (mean +/- SEM, range 2.35-6.38 mmol/12 h), indicating that an overnight urinary Ca of < 2.35 mmol/12 h (< 60% of the overnight urinary Ca distribution) ruled out the possibility of finding hypercalciuria in 24-hour urine. Fourteen of the seventeen hypercalciuric men had overnight urinary Ca in the upper 20% of the distribution (> or = 3.25 mmol/12 h). Hypercalciuria was found in 14 of the 19 men (73.7%) with an overnight urinary Ca of > or = 3.25 mmol/12 h, but only in 3 of the 81 men (3.7%) with an overnight urinary Ca of < 3.25 mmol/12 h.(ABSTRACT TRUNCATED AT 250 WORDS)
To investigate indices of calcium (Ca) homeostasis in celiac disease (CD).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).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.Overt and subclinical CD is associated with low urinary Ca excretion under fed condition, which relates to low intestinal absorption.
Several studies have reported that high sodium (Na) intake increases not only urinary Na but also urinary calcium (Ca), suggesting that high Na intake could be involved in the pathogenesis of hypercalciuria. No research data are available on the relationship of Na intake to the prevalence of hypercalciuria within the general population. Moreover, it is not clear if Na intake relates only to urinary Ca or also to other indices of Ca homeostasis, including intestinal Ca absorption. In the present paper, two distinct studies addressed these points using 24-hour urinary Na as an index of salt intake in individuals on their habitual unrestricted free diet. Study 1 analyzed the relationship between 24-hour urinary Na and hypercalciuria (24-hour urinary Ca > or = 7.5 mmol in men, > or = 6.25 mmol in women) in a population sample of 203 men and women, aged 20-59 years. Study 2 analyzed the relationship between 24-hour urinary Na and intestinal strontium (Sr) absorption, used as an index of intestinal Ca absorption, urinary (24-hour and fasting) and plasma Ca, and plasma parathyroid hormone in 36 healthy men and women, aged 18-65 years. Within the population sample (study 1), 24-hour urinary Na was directly and significantly correlated with prevalence of hypercalciuria when controlling for gender, age, weight, and urinary creatinine: the relationship was continuous and linear for urinary Na ranging between 40 and 200 mmol/24 h. In the 36 volunteers (study 2), 24-hour urinary Na was related to 24-hour and fasting urinary Ca (p < 0.001) but not to intestinal Sr absorption: the relationship between 24-hour urinary Na and urinary Ca (both 24 h and fasting) was also significant, controlling for other variables. The results indicate that in adults on their habitual diet, urinary Na, which reflects dietary salt intake, correlates with the prevalence of hypercalciuria independently of intestinal Ca absorption and mainly via renal mechanisms.
