Final answer:
Decreased potassium excretion can occur due to renal dysfunction such as renal failure, Addison's disease which affects aldosterone production, and alkalosis leading to potassium redistribution.
Step-by-step explanation:
Some causes of decreased potassium excretion include renal dysfunction, such as renal failure, which leads to a decrease in glomerular filtration rate, thus affecting the kidneys' ability to excrete potassium effectively. Conditions like Addison's disease reduce the body's production of aldosterone, which in turn lowers the rate of potassium excretion by the kidneys. Contrary to increased aldosterone levels which lead to higher potassium excretion, decreased aldosterone levels have the opposite effect. Additionally, alkalosis can contribute to a relative reduction in serum potassium levels due to the redistribution of potassium from the extracellular to intracellular space, though it does not decrease total body potassium.