a Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine , Utrecht University , Utrecht , The Netherlands.
Vet Q. 2018 Dec;38(1):72-78. doi: 10.1080/01652176.2018.1521537.
In dogs, spontaneous Cushing's syndrome is most often pituitary-dependent and caused by hypersecretion of adrenocorticotropic hormone (ACTH), resulting in increased adrenocortical glucocorticoid secretion similar to horses. In horses with Cushing's syndrome (or pituitary pars intermedia dysfunction [PPID]) a thyrotropin-releasing hormone (TRH) stimulation test can be used for diagnosis, as TRH administration results in increased circulating ACTH and cortisol concentrations in affected horses.
The aim of this study was to investigate the effect of TRH administration on the circulating ACTH and cortisol concentrations in dogs with pituitary-dependent hypercortisolism (PDH).
Ten clinically normal control dogs and 10 dogs with PDH, all client owned, underwent a TRH stimulation test with measurement of plasma concentrations of ACTH and cortisol, before and after intravenous administration of 10 μg TRH/kg bodyweight.
Plasma ACTH concentration did not rise significantly after TRH stimulation, neither in PDH dogs nor in clinically normal dogs. In contrast, the plasma cortisol concentration did increase significantly after TRH stimulation in both groups (p = .003 in PDH and p < .001 in control). Immunohistochemistry of normal adrenal glands demonstrated the presence of TRH receptors in the whole adrenal cortex.
The results of this study demonstrate that the TRH stimulation test should be rejected as a tool to diagnose PDH in dogs. The observed TRH-induced increase in plasma cortisol concentration without a significant rise in plasma ACTH concentration may be explained by a direct effect of TRH on adrenocortical cells mediated by adrenocortical TRH receptors.
在犬中，自发性库欣综合征通常是垂体依赖性的，由促肾上腺皮质激素（ACTH）过度分泌引起，导致肾上腺皮质糖皮质激素分泌增加，类似于马。在患有库欣综合征（或垂体中间部分功能障碍[PPID]）的马中，可以使用促甲状腺素释放激素（TRH）刺激试验进行诊断，因为 TRH 给药会导致受影响的马循环中的 ACTH 和皮质醇浓度增加。
本研究旨在研究 TRH 给药对垂体依赖性高皮质醇血症（PDH）犬循环 ACTH 和皮质醇浓度的影响。
10 只临床正常对照犬和 10 只 PDH 犬（均为客户所有）接受了 TRH 刺激试验，测量了 ACTH 和皮质醇的血浆浓度，在静脉注射 10μg/kg 体重 TRH 前后。
TRH 刺激后，PDH 犬和临床正常犬的血浆 ACTH 浓度均未显著升高。相比之下，两组的血浆皮质醇浓度在 TRH 刺激后均显著升高（PDH 组 p=0.003，对照组 p<0.001）。正常肾上腺的免疫组织化学显示整个肾上腺皮质存在 TRH 受体。
本研究结果表明，TRH 刺激试验不应作为诊断犬 PDH 的工具。观察到的 TRH 诱导的血浆皮质醇浓度增加而血浆 ACTH 浓度没有显著升高，可能是 TRH 通过肾上腺皮质 TRH 受体直接作用于肾上腺皮质细胞所致。
