Normal calcium
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Understanding Normal Calcium Levels: Insights from Recent Research
Normal Serum Calcium Levels by Atomic Absorption Spectroscopy
Normal adult calcium levels have been established using the atomic absorption spectrophotometric technique. This method revealed significant differences in calcium concentration between sexes. Additionally, three commonly employed serum treatment techniques were compared, with two yielding equivalent results.
Calcium Fractions in Normal Serum
Research has identified the different fractions of calcium in normal serum. Using ultrafiltration and a calcium-sensitive electrode, it was found that the mean values for ultrafiltrable calcium were 1.53 mM/L, accounting for 59% of the total calcium. Protein-bound calcium was measured at 1.07 mM/L, making up 41% of the total calcium. Within the ultrafiltrable fraction, ionic calcium was 1.16 mM/L (45% of the total), and complexed calcium was 0.37 mM/L (14% of the total).
Serum Ionized Calcium Measurement
The concentration of serum ionized calcium ([Ca2+]) in normal individuals was measured using a calcium-selective electrode. The mean value was found to be 1.06 mmol/L, with a range of 0.97 to 1.13 mmol/L. This method proved to be reproducible and sensitive, showing no significant correlation with age or sex.
Calcium Balance and Requirements in Middle-Aged Women
A study on 130 perimenopausal women aged 35 to 50 evaluated calcium balance using two distinct methods. Both methods showed that women on higher self-selected calcium intakes had a more positive calcium balance. The study suggested that an intake of 1.241 g/day is required to achieve a zero calcium balance, which is higher than the current recommended dietary allowance.
Genetic Factors Influencing Serum Calcium
A genome-wide association meta-analysis identified six new loci associated with serum calcium concentrations. These loci include regions near genes involved in calcium homeostasis and bone density, such as CYP24A1, GATA3, and DGKD. This research highlights the genetic underpinnings of calcium regulation in the body.
Intestinal Calcium Absorption and Vitamin D
Intestinal calcium absorption decreases with age, as shown in a study involving 94 normal subjects. In postmenopausal osteoporotic patients, calcium absorption was significantly lower. The study also found a positive correlation between calcium absorption and serum 1,25-dihydroxyvitamin D levels in normal subjects. However, this correlation was absent in elderly subjects and osteoporotic patients, suggesting an age-related decline in the metabolism of vitamin D.
Adjusting Calcium Concentration in Patients with Abnormal Serum Proteins
In patients with abnormal serum proteins, calcium concentration closely correlated with albumin levels. A formula was derived to adjust calcium concentration based on albumin levels, ensuring that adjusted calcium levels fell within the normal range.
High-Normal Calcium Dialysate in CAPD Patients
For patients on continuous ambulatory peritoneal dialysis (CAPD), using a high-normal calcium dialysate (1.35 mmol/L) effectively controlled plasma calcium, phosphate, and parathyroid hormone levels. This approach minimized the risk of hypercalcemia and reduced the need for aluminum-containing phosphate binders.
Conclusion
Understanding normal calcium levels and their regulation is crucial for maintaining overall health. Recent research has provided valuable insights into the normal ranges of serum calcium, the impact of dietary intake, genetic factors, and the role of vitamin D. These findings are essential for developing effective strategies to manage calcium-related disorders and ensure optimal calcium balance in various populations.
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