Hinrichsen Sophia L, Yuen Ka Y, Dryburgh Elizabeth L, Bertin François-René, Stewart Allison J
School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
Boehringer Ingelheim Animal Health Australia Pty. Ltd., North Ryde, NSW 2113, Australia.
Animals (Basel). 2022 Jan 28;12(3):324. doi: 10.3390/ani12030324.
Pituitary pars intermedia dysfunction (PPID) is diagnosed by increased basal or post thyrotropin-releasing hormone (TRH) stimulation ACTH concentrations. ACTH is known to be unstable; however, the effect of different temperatures and TRH stimulation on equine ACTH stability is poorly described. In total, 15 horses, including 8 PPID positive (ACTH > 35 pg/mL at baseline or >65 pg/mL 30 min after TRH stimulation), were divided into 2 groups: 9, including 5 PPID positive, with basal ACTH concentrations and 6, including 3 PPID positive, with post TRH stimulation ACTH concentrations. Whole blood was stored for 1 h at 4, 20, 30, 40, or 70 °C. After centrifugation, immunoreactive ACTH concentrations were determined using a chemiluminescent assay. Linear mixed effect models were used to detect the effects of temperature, PPID status, and TRH stimulation on the immunoreactive ACTH concentration. Temperature had a significant effect ( = 0.003) on immunoreactive ACTH concentrations, and this effect was greater in PPID-negative horses ( = 0.01), with the changes in immunoreactive ACTH concentrations being slightly unpredictably higher or lower than samples stored at 4 °C. Even at 20 °C, mean immunoreactive ACTH concentrations minimally changed by 5% in PPID horses and 12% in non-PPID horses after 1 h. No significant effect of TRH stimulation was identified. Although ACTH concentrations should ideally be determined from samples kept at 4 °C, samples inadvertently left at temperatures of up to 40 °C can provide valid results if analyzed within 1 h; however, this increases the risks of altered ACTH concentrations, occasionally influencing the diagnosis of PPID.
垂体中间部功能障碍（PPID）通过基础促肾上腺皮质激素（ACTH）浓度升高或促甲状腺激素释放激素（TRH）刺激后ACTH浓度升高来诊断。已知ACTH不稳定；然而，不同温度和TRH刺激对马ACTH稳定性的影响描述甚少。总共15匹马，包括8匹PPID阳性马（基线ACTH>35 pg/mL或TRH刺激后30分钟ACTH>65 pg/mL），被分为两组：9匹，包括5匹PPID阳性马，检测基础ACTH浓度；6匹，包括3匹PPID阳性马，检测TRH刺激后ACTH浓度。全血在4、20、30、40或70℃下保存1小时。离心后，使用化学发光分析法测定免疫反应性ACTH浓度。采用线性混合效应模型检测温度、PPID状态和TRH刺激对免疫反应性ACTH浓度的影响。温度对免疫反应性ACTH浓度有显著影响（P = 0.003），且这种影响在PPID阴性马中更大（P = 0.01），免疫反应性ACTH浓度的变化比4℃保存的样本略高或略低，难以预测。即使在20℃下，1小时后PPID马的免疫反应性ACTH平均浓度变化最小为5%，非PPID马为12%。未发现TRH刺激有显著影响。虽然理想情况下ACTH浓度应从4℃保存的样本中测定，但如果在1小时内进行分析，无意中保存在高达40℃温度下的样本也可提供有效结果；然而，这会增加ACTH浓度改变的风险，偶尔会影响PPID的诊断。
