What condition can cause a decrease in glomerular filtration rate (GFR)?

Dehydration is indeed a condition that can lead to a decrease in glomerular filtration rate (GFR). When an individual is dehydrated, there is a reduction in blood volume and subsequently a decrease in renal perfusion. This low blood flow to the kidneys triggers several compensatory mechanisms, one of which is the constriction of the afferent arterioles to preserve glomerular filtration. However, if the dehydration is severe, the overall GFR can decrease due to insufficient fluid reaching the glomeruli, ultimately impairing the kidneys' ability to filter waste effectively.

In contrast, other conditions like hypertension may initially increase GFR by increasing renal blood flow, although long-term uncontrolled hypertension may lead to kidney damage. Infection could impact GFR through inflammation or obstruction, but it is not a direct cause of decreased GFR like dehydration. Excess fluid intake typically increases GFR by expanding blood volume and renal perfusion, stimulating the kidneys to filter more blood to maintain homeostasis. Thus, dehydration is the most direct and immediate cause of decreased GFR among the options presented.