Hyponatremia and SIADH
======================

* Simon Smitz

In their article on hyponatremia,1 Haralampos Milionis and colleagues do not mention an interesting diag-nostic tool: the detection of high- molecular-weight forms of vasopressin. The presence of this in plasma, sometimes in large amounts, is highly suggestive of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with a carcinoma of the lung.2,3,4

**Simon Smitz** Department of Internal Medicine University of Liège Liège, Belgium

## References

1.  1. Milionis HJ, Liamis GL, Elisaf MS. The hyponatremic patient: a systematic approach to laboratory diagnosis. CMAJ 2002;166(8):1056-62.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czoxMDoiMTY2LzgvMTA1NiI7czo0OiJhdG9tIjtzOjIyOiIvY21hai8xNjcvNS80NDkuMy5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

2.  2. Yamaji T, Ishibashi M, Hori T. Propressophysin in human blood: a possible marker of ectopic vasopressin production. J Clin Endocrinol Metab 1984; 59:505-12.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1210/jcem-59-3-505&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=6086701&link_type=MED&atom=%2Fcmaj%2F167%2F5%2F449.3.atom) 
    
    [Web of Science](http://www.cmaj.ca/lookup/external-ref?access_num=A1984TE97500025&link_type=ISI) 

3.  3. Smitz S, Legros JJ, Franchimont P, le Maire M. High molecular weight vasopressin: detection of a large amount in the plasma of a patient. *Clin Endocrinol (Oxf)* 1985;23:379-84.
    
    

4.  4. Mizobuchi M, Kunishige M, Kubo K, Komatsu M, Bando H, Saito S. Syndrome of inappropriate secretion of ADH (SIADH) due to small cell lung cancer with extremely high plasma vasopressin level. Intern Med 1994;33:501-4.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.2169/internalmedicine.33.501&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=7803920&link_type=MED&atom=%2Fcmaj%2F167%2F5%2F449.3.atom)