Comparison of serum parathyroid hormone and ionized calcium and magnesium concentrations and fractional urinary clearance of calcium and phosphorus in healthy horses and horses with enterocolitis.

This study evaluates the calcium balance and parathyroid gland function in healthy horses and horses with enterocolitis, using both immunochemiluminometric and immunoradiometric assays for determining serum parathyroid hormone concentrations. The findings reveal that horses with enterocolitis often exhibited reduced serum total calcium, ionized calcium, and magnesium concentrations along with an increase in phosphorus concentrations, suggesting a link between enterocolitis and hypocalcemia.

Research Methodology

• The study involved both healthy horses as well as those with enterocolitis, specifically including 64 horses with enterocolitis and 62 healthy ones.
• Blood and urine samples were taken from the subjects to determine the levels of various substances such as total calcium, ionized calcium, magnesium, phosphorus, BUN, total protein, creatinine, albumin, and parathyroid hormone concentrations. Additionally, venous blood gases were observed, and the fractional urinary clearance of calcium and phosphorus was assessed.
• For measurement of serum concentrations of parathyroid hormone, both an immunoradiometric assay (IRMA) and an immunochemiluminometric assay (ICMA) were utilized, with these techniques being applied for 40 horses in total.

Research Findings

• Most of the horses diagnosed with enterocolitis, precisely 48 out of the 64, showed lower concentrations of total calcium, ionized calcium, and magnesium in the serum. By contrast, they displayed increased phosphorus concentrations, in comparison to healthy horses.
• The concentration of serum parathyroid hormone was found to be increased in most of the horses with hypocalcemia, realized in 36 out of the 51 horses thus presenting.
• The fractional urinary clearance of calcium was significantly lower in horses with enterocolitis, whereas their fractional urinary clearance of phosphorus was significantly higher, when compared to healthy horses.
• The ICMA findings were consistent with the IRMA results.

Conclusions

• The study concludes that there is often an association between enterocolitis in horses and hypocalcemia, as 79.7% of the afflicted horses had ionized hypocalcemia.
• As the fractional urinary clearance of calcium was low in these horses, the study proposes that renal calcium loss is unlikely the cause of hypocalcemia.
• The study also observes varying serum parathyroid hormone concentrations in horses with enterocolitis and concurrent hypocalcemia. Nonetheless, the authors opine that the low parathyroid hormone concentration in some hypocalcemic horses may be due to impaired parathyroid gland function.