College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; Faculty of Veterinary Medicine, University of Sadat City, Sadat City, Egypt.
College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA.
Domest Anim Endocrinol. 2020 Jul;72:106470. doi: 10.1016/j.domaniend.2020.106470. Epub 2020 Mar 6.
Hypocalcemia is a common finding in critically ill equine patients. Parathyroid hormone (PTH) helps to maintain calcium homeostasis in hypocalcemic patients by promoting renal calcium reabsorption and bone resorption. Increased serum PTH concentrations have been reported in critically ill people and animals, including horses and foals. It is unknown whether increased secretion of PTH is associated with markers of bone turnover in hospitalized foals. The goals of this study were to measure markers of bone resorption (C-terminal telopeptide of type I collagen [CTX-I]) and bone formation (osteocalcin [OCN]; alkaline phosphatase [ALP]) and to determine their association with PTH concentrations, disease severity, and mortality in hospitalized foals. This prospective, multicenter, cross-sectional study was conducted on 75 newborn foals ≤3 d old divided into hospitalized (n = 65; 41 septic; 24 sick nonseptic) and healthy (n = 10) groups. Blood samples were collected on admission to measure serum CTX-I, OCN, and PTH concentrations and ALP activity. Data were analyzed by nonparametric methods and univariate logistic regression. Serum CTX-I and PTH concentrations were significantly higher, whereas OCN concentrations were lower, in septic compared with healthy foals (P < 0.05). Serum ALP activity was not different between groups; however, it was lower in hospitalized and septic foals with low OCN concentrations (P < 0.05). In hospitalized foals, PTH concentrations were positively correlated with CTX-I concentrations and inversely associated with ALP activity (P < 0.05). High CTX-I and low OCN concentrations were associated with disease severity (P < 0.05). Hospitalized nonsurviving foals had significantly lower OCN concentrations compared with survivors (P < 0.05), but CTX-I concentrations were not associated with survival. Hospitalized foals with PTH concentrations >12.4 pmol/L were more likely to die (OR = 1.5; 95% CI = 1.1-4.16; P < 0.05). Elevated PTH and CTX-I together with reduced OCN concentrations and ALP activity in sick foals indicates that bone resorption is increased during critical illness, which may be a compensatory mechanism to correct hypocalcemia or reflect a response to systemic inflammation and metabolic imbalances. Bone resorption could negatively impact skeletal development in the growing foal. Low OCN and high PTH concentrations were predictors of nonsurvival in hospitalized foals.
低钙血症是危重病马的常见表现。甲状旁腺激素（PTH）通过促进肾脏钙重吸收和骨吸收来帮助维持低钙血症患者的钙稳态。在危重病患者和动物中，包括马和驹，已报告血清 PTH 浓度增加。尚不清楚 PTH 的分泌增加是否与住院驹的骨转换标志物有关。本研究的目的是测量骨吸收标志物（I 型胶原 C 端肽[CTX-I]）和骨形成标志物（骨钙素[OCN]；碱性磷酸酶[ALP]），并确定它们与住院驹的 PTH 浓度、疾病严重程度和死亡率的关系。这项前瞻性、多中心、横断面研究共纳入 75 头≤3 日龄的新生驹，分为住院（n=65；41 例败血症；24 例非败血症性疾病）和健康（n=10）两组。入院时采集血样，以测量血清 CTX-I、OCN 和 PTH 浓度和 ALP 活性。采用非参数方法和单变量逻辑回归进行数据分析。败血症驹的血清 CTX-I 和 PTH 浓度显著高于健康驹，而 OCN 浓度则低于健康驹（P＜0.05）。各组间血清 ALP 活性无差异；然而，在低 OCN 浓度的住院和败血症驹中，ALP 活性较低（P＜0.05）。在住院驹中，PTH 浓度与 CTX-I 浓度呈正相关，与 ALP 活性呈负相关（P＜0.05）。高 CTX-I 和低 OCN 浓度与疾病严重程度相关（P＜0.05）。住院未存活驹的 OCN 浓度明显低于存活驹（P＜0.05），但 CTX-I 浓度与存活无关。PTH 浓度＞12.4 pmol/L 的住院驹更有可能死亡（OR=1.5；95%CI=1.1-4.16；P＜0.05）。在患病驹中，PTH 和 CTX-I 升高，OCN 浓度和 ALP 活性降低，表明在危重病期间骨吸收增加，这可能是纠正低钙血症的代偿机制，或反映对全身炎症和代谢失衡的反应。骨吸收可能会对生长中的驹的骨骼发育产生负面影响。低 OCN 和高 PTH 浓度是住院驹存活的预测指标。
