Nigro Nicole, Grossmann Mathis, Chiang Cherie, Inder Warrick J
Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
Department of Medicine, Austin Health, University of Melbourne, Melbourne, Victoria, Australia.
Intern Med J. 2018 Mar;48(3):244-253. doi: 10.1111/imj.13627.
The main determinants for the maintenance of water homeostasis are the hormone arginine vasopressin (AVP) and thirst. Disturbances in these regulatory mechanisms can lead to polyuria-polydipsia syndrome, which comprises of three different conditions: central diabetes insipidus (DI) due to insufficient secretion of AVP, nephrogenic DI caused by renal insensitivity to AVP action and primary polydipsia due to excessive fluid intake and consequent physiological suppression of AVP. It is crucial to determine the exact diagnosis because treatment strategies vary substantially. To differentiate between the causes of the polyuria-polydipsia syndrome, a water deprivation test combined with desmopressin administration is the diagnostic 'gold standard'. Thereby, AVP activity is indirectly evaluated through the measurement of urine osmolality after prolonged dehydration. However, this test has several limitations and may fail to distinguish precisely between patients with primary polydipsia and mild forms of central and nephrogenic DI. The direct measurement of AVP during the water deprivation test, which was reported in the 1980s, has not been widely adopted due to availability, assay issues and diagnostic performance. Recently, copeptin, the c-terminal portion of the larger precursor peptide of AVP, has been evaluated in the setting of polyuria-polydipsia syndrome and appears to be a useful candidate biomarker for the differential diagnosis. A standardised method for the water deprivation test is presented as part of a joint initiative of the Endocrine Society of Australia, the Australasian Association of Clinical Biochemists and the Royal College of Pathologists of Australasia to harmonise dynamic endocrine tests across Australia.
维持水稳态的主要决定因素是精氨酸加压素（AVP）和口渴感。这些调节机制的紊乱可导致多尿-多饮综合征，该综合征包括三种不同情况：由于AVP分泌不足导致的中枢性尿崩症（DI）、因肾脏对AVP作用不敏感引起的肾性尿崩症以及因液体摄入过多和随之而来的AVP生理性抑制导致的原发性烦渴。确定确切诊断至关重要，因为治疗策略差异很大。为了区分多尿-多饮综合征的病因，禁水试验联合去氨加压素给药是诊断的“金标准”。通过长时间脱水后测量尿渗透压来间接评估AVP活性。然而，该试验有几个局限性，可能无法准确区分原发性烦渴患者与轻度中枢性和肾性尿崩症患者。20世纪80年代报道的在禁水试验期间直接测量AVP的方法，由于可用性、检测问题和诊断性能等原因尚未被广泛采用。最近，copeptin（AVP较大前体肽的C末端部分）已在多尿-多饮综合征的背景下进行评估，似乎是鉴别诊断的一个有用候选生物标志物。作为澳大利亚内分泌学会、澳大利亚临床生物化学家协会和澳大利亚皇家病理学家学院联合倡议的一部分，提出了一种标准化的禁水试验方法，以协调澳大利亚各地的动态内分泌检测。
