Acid and Base Balance
Syndrome of Inappropriate Antidiuretic Hormone
What's SIADH?
SIADH is the syndrome of inappropriate antidiuretic hormone. Normally, the antidiuretic hormone (ADH) is a hormone released by the hypothalamus, stored in the posterior pituitary gland and released whenever the hypothalamus senses a need to keep more water in the body, or you are thirsty. ADH flows through the bloodstream to the kidneys that then start to keep water in your body. When SIADH occurs there is an excess of ADH that retains water, while urine output does not increase, resulting in an electrolyte imbalance, hyponatremia or low sodium concentration. (Society for Endocrinology (SE), 2015)
Image © Eleni Papachristou
Who does this effect?
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SIADH caused hyponatremia is among the common electrolyte imbalances in clinical practice, and prevalent most often with nursing home residents, the elderly and cancer patients. (Shepshelovich et al. 2015, Introduction section, papa. 1,2)
ADH Pathway
ADH is made in the Hypothalamus and stored in the Posterior Pituitary Gland. Sensors in the Hypothalamus notify the Posterior Pituitary to release ADH if blood volume is reduced, or we feel thirsty. ADH then travels through the bloodstream to the kidneys. ADH signals the kidney to retain more water .
ADH
Image © Eleni Papachristou
Why does this happen?
The most common causes of SIADH etiologies are malignancies and medication-induced, followed by idiopathic SIADH, pulmonary infections, pain and nausea, and CNS disorders. CNS disorders typically present the most severe. (Shepshelovich et al. 2015, Discussion section, papa 1)
What are the symptoms?
Acute hyponatremia is a medical emergency but very few SIADH cases present that way. In some cases the symptoms are even initially undetectable. Early symptoms that would be present are not specific to SIADH and so may be hard to diagnose and include, nausea, vomiting, cramping and dislike of water. More advanced symptoms may include edema, confusion, coma, convulsions, autonomic manifestation and without being treated could ultimately lead to death. (Frouget, 2012, Clinic section, papa. 1)
How is it treated?
Treatment is individual to each patient as teach case of SIADH may be reached due to a different issue. Treatments may include: hypertonic saline solution, water restriction, demeclocycline, furosemide, urea and receptor inhibitor vasopressin. (Frouget, 2012, Treatment section)
References:
Frouget, T. (2012) The syndrome of inappropriate antidiuresis. Internal Medicine Journal, 33(10), 556-566. http://dx.doi.org.authenticate.library.duq.edu/10.1016/j.revmed.2012.07.005
Shepshelovich, D., Leibovitch, C., Klein, A., Zoldan, S., Milo, G., Shochat, T., Rozen-zvi, B., Gafter-Gvili, A., & Lahav, M. (2015). The syndrome of inappropriate antidiuretic hormone secretion: Distribution and characterization according to etiologies. European Journal of Internal Medicine. 26(10).819-824. http://dx.doi.org.authenticate.library.duq.edu/10.1016/j.ejim.2015.10.020
Society for Endocrinology (2015) Anti-diuretic hormone. (n. p.). Retrieved from http://www.yourhormones.info/hormones/antidiuretic_hormone.aspx
This tab was created on October 16, 2016
Last edited on October 23, 2016