causes for a decrease in bun
Factors that Decrease BUN. 1  Low-protein diet, malnutrition or starvation (R). 2  Impaired liver activity due to liver disease (R). 3  Genetic deficiency of urea cycle enzymes (R). 4  Higher IGF-1 and growth hormone. 5  Anabolic steroids, which decreases protein breakdown. 6  Overhydration, or drinking a lot of water. 7  Pregnancy (due to increased plasma volume) (R).