What does aldosterone suppression in SIADH cause in terms of sodium levels?

In the context of SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion), aldosterone suppression plays a critical role in sodium homeostasis. Normally, aldosterone promotes renal reabsorption of sodium in the kidneys, which helps to regulate sodium levels in the bloodstream. However, in SIADH, there is an inappropriate secretion of antidiuretic hormone (ADH), leading to excess water retention and dilution of serum sodium levels.

When aldosterone is suppressed, the reabsorption of sodium is impaired, which further contributes to a decrease in serum sodium concentrations. This suppression leads to a situation where the body is absorbing excess water, while sodium is not retained adequately, resulting in hyponatremia, or decreased sodium levels. Consequently, the sodium levels in the body drop, consistent with the characteristics of SIADH, where the dilutional effect of excess water leads to low sodium levels.