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.

低钙血症是重症马科动物的常见发现。甲状旁腺激素（PTH）通过促进肾钙的重吸收和骨吸收来帮助维持低钙血症患者的钙稳态。据报道，重症患者和动物，包括马和驹，血清PTH浓度升高。尚不清楚PTH分泌的增加是否与住院小马驹的骨转换标志有关。这项研究的目的是测量骨吸收（I型胶原的C端端肽[CTX-I]）和骨形成（骨钙蛋白[OCN]；碱性磷酸酶[ALP]）的标志物，并确定它们与PTH浓度的关系，住院小马驹的疾病严重程度和死亡率。这个前瞻性的多中心 对75只≤3 d的新生小马进行了横断面研究，分为住院组（n = 65； 41个败血症； 24个病态非败血症）和健康组（n = 10）。入院时采集血样以测量血清CTX-1，OCN和PTH浓度以及ALP活性。通过非参数方法和单因素逻辑回归分析数据。与健康小马驹相比，化粪池中的血清CTX-1和PTH浓度显着较高，而OCN浓度较低（P <0.05）。两组之间的血清ALP活性无差异。但是，在低OCN浓度的住院和化脓小马驹中，这一比例较低（P <0.05）。在住院小马驹中，PTH浓度与CTX-1浓度呈正相关，与ALP活性呈负相关（P <0.05）。高CTX-1和低OCN浓度与疾病严重程度相关（P <0.05）。与幸存者相比，住院的未存活小马驹的OCN浓度明显较低（P <0.05），但CTX-1浓度与存活率无关。PTH浓度> 12.4 pmol / L的住院小马驹更容易死亡（OR = 1.5； 95％CI = 1.1–4.16；P<0.05）。PTH和CTX-I升高，患病小马驹的OCN浓度和ALP活性降低，表明严重疾病期间骨吸收增加，这可能是纠正低钙血症或反映对全身炎症和代谢失衡反应的补偿机制。骨骼吸收可能会对生长的小马驹的骨骼发育产生负面影响。低OCN和高PTH浓度是住院马驹无法存活的预测因素。