Melbourne Veterinary School, The Universtiy of Melbourne, Building 400, Parkville, Victoria 3010, Australia.
School of Veterinary Science, The University of Queensland, Building 4114, Gatton, Queensland 4343, Australia.
Vet J. 2023 Jun-Jul;296-297:105995. doi: 10.1016/j.tvjl.2023.105995. Epub 2023 May 18.
Plasma adrenocorticotropic hormone (ACTH) concentration is commonly measured to diagnose pituitary pars intermedia dysfunction (PPID). Several intrinsic and extrinsic factors affect ACTH concentrations, including breed. The objective of this study was to prospectively compare plasma ACTH concentrations among different breeds of mature horses and ponies. Three breed groups comprised Thoroughbred horses (n = 127), Shetland ponies (n = 131) and ponies of non-Shetland breeds (n = 141). Enrolled animals did not show any signs of illness, lameness or clinical signs consistent with PPID. Blood samples were collected 6 months apart, around the autumn equinox and spring equinox, and plasma concentrations of ACTH were measured by chemiluminescent immunoassay. Pairwise breed comparisons within each season were performed on log transformed data using the Tukey test. Estimated mean differences in ACTH concentrations were expressed as fold difference with 95 % confidence intervals (CI). Reference intervals for each breed group per season were calculated using non-parametric methods. In autumn, higher ACTH concentrations were found among non-Shetland pony breeds compared with Thoroughbreds (1.55 fold higher; 95 % CI, 1.35-1.77; P < 0.001), and in Shetland ponies compared with Thoroughbreds (2.67 fold higher; 95 % CI, 2.33-3.08; P < 0.001) and non-Shetland pony breeds (1.73 fold higher; 95 % CI, 1.51-1.98; P < 0.001). In spring, no differences were identified among breed groups (all P > 0.05). Reference intervals were similar among breed groups in spring, but upper limits for ACTH concentrations were markedly different between Thoroughbred horses and pony breeds in autumn. These findings emphasise that breed should be accounted for when determining and interpreting reference intervals for ACTH concentrations among healthy horses and ponies in autumn.
血浆促肾上腺皮质激素（ACTH）浓度常用于诊断脑垂体中间部功能减退症（PPID）。有几种内在和外在因素会影响 ACTH 浓度，包括品种。本研究的目的是前瞻性比较不同品种成年马和小马的血浆 ACTH 浓度。三个品种组包括纯种马（n=127）、设得兰矮种马（n=131）和非舍特兰矮种马品种（n=141）。入组动物没有出现任何疾病、跛行或与 PPID 一致的临床症状。在秋分和春分前后，每隔 6 个月采集一次血液样本，并通过化学发光免疫测定法测量血浆 ACTH 浓度。在每个季节，使用 Tukey 检验对原始数据进行了种间比较。用 95%置信区间（CI）表示 ACTH 浓度的平均差异倍数。使用非参数方法计算每个季节每个品种组的参考区间。在秋季，非设得兰矮种马品种的 ACTH 浓度明显高于纯种马（高 1.55 倍；95%CI，1.35-1.77；P<0.001），也明显高于设得兰矮种马（高 2.67 倍；95%CI，2.33-3.08；P<0.001）和非设得兰矮种马品种（高 1.73 倍；95%CI，1.51-1.98；P<0.001）。在春季，品种间没有差异（所有 P>0.05）。在春季，品种间的参考区间相似，但在秋季，纯种马和小马品种之间 ACTH 浓度的上限差异显著。这些发现强调，在确定和解释秋季健康马和小马的 ACTH 浓度参考区间时，应考虑品种因素。
