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This Article Full Text Full Text (PDF) All Versions of this Article: 287/5/E1019    most recent 00033.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Smith, D. Articles by Thompson, C. J. Search for Related Content PubMed PubMed Citation Articles by Smith, D. Articles by Thompson, C. J.

Downward resetting of the osmotic threshold for thirst in patients with SIADH

Departments of ¹Endocrinology and ²Chemical Pathology, Beaumont Hospital, Dublin 9, Ireland; and ³Department of Endocrinology, Royal Victoria Infirmary, Newcastle-upon-Tyne NE1 4LP, United Kingdom

Submitted 23 January 2004 ; accepted in final form 13 June 2004

The syndrome of inappropriate antidiuretic hormone (SIADH) is characterized by euvolemic hyponatremia. Patients with SIADH continue to drink normal amounts of fluid, despite plasma osmolalities well below the physiological osmotic threshold for onset of thirst. The regulation of thirst has not been previously studied in SIADH. We studied the characteristics of osmotically stimulated thirst and arginine vasopressin (AVP) secretion in eight subjects with SIADH and eight healthy controls and the nonosmotic suppression of thirst and AVP during drinking in the same subjects. Subjects underwent a 2-h infusion of hypertonic (855 mmol/l) NaCl solution, followed by 30 min of free access to water. Thirst rose significantly in both SIADH (1.5 ± 0.6 to 8.0 ± 1.2 cm, P < 0.0001) and controls (1.8 ± 0.8 to 8.4 ± 1.5 cm, P < 0.0001), but the osmotic threshold for thirst was lower in SIADH (264 ± 5.5 vs. 285.9 ± 2.8 mosmol/kgH₂O, P < 0.0001). SIADH subjects drank volumes of water similar to controls after cessation of the infusion (948.8 ± 207.6 vs. 1,091 ± 184 ml, P = 0.23). The act of drinking suppressed thirst in both SIADH and controls but did not suppress plasma AVP concentrations in SIADH compared with controls (P = 0.007). We conclude that there is downward resetting of the osmotic threshold for thirst in SIADH but that thirst responds to osmotic stimulation and is suppressed by drinking around the lowered set point. In addition, we demonstrated that drinking does not completely suppress plasma AVP in SIADH.

syndrome of inappropriate antidiuretic hormone; arginine vasopressin; hyponatremia

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