Post-doc student College of Veterinary Medicine, The Ohio State University Columbus, Ohio, United States
Abstract:
Background: Hypocalcemia has been documented in horses with gastrointestinal disease and colitis. PTH maintains calcium homeostasis during hypocalcemia by enhancing bone resorption and renal calcium reabsorption. Markers of bone remodeling include C-terminal telopeptide of type I collagen (CTX-I; resorption) and osteocalcin (OCN; formation). The skeletal response to hypocalcemia and high PTH concentrations has not been evaluated in critically ill horses.
Objectives: To measure markers of bone resorption (CTX-I) and formation (OCN) and to determine their association with serum PTH, total calcium (tCa), ionized calcium (iCa) and phosphorus concentrations, disease severity, and mortality in horses with colitis.
Methods: Prospective, multicenter. 70 horses (55 with colitis and 15 healthy) were included. Blood samples were collected on admission. Serum CTX-I, OCN, and PTH concentrations were measured by immunoassays. Data were analyzed by non-parametric methods and univariate analysis.
Results: Serum CTX-1 and PTH concentrations were higher, while serum OCN, tCa, iCa and phosphorus concentrations were lower in horses with colitis compared to healthy ones (P< 0.05). Serum tCa and iCa concentrations were lower and PTH higher in non-surviving horses with colitis (P< 0.05). Horses with PTH concentrations >139.9 pg/mL were more likely to die (OR = 2.9; P< 0.05).
Conclusions: Increased PTH and CTX-I together with reduced OCN, tCa, iCa and phosphorus concentrations in horses with colitis are consistent with increased bone turnover to restore normocalcemia. Excessive PTH response was associated with mortality, suggesting PTH resistance. Elevated PTH and reduced iCa concentrations predicted mortality with fair sensitivity and specificity in horses with colitis.
