Elevated levels of which metabolite are indicative of vitamin B12 deficiency?

Elevated levels of which metabolite are indicative of vitamin B12 deficiency?

• A. Methylmalonic acid
• B. Homocysteine
• C. Ferritin
• D. Cobalamin

Answer: (A)

Elevated methylmalonic acid indicates vitamin B12 deficiency because B12 is a cofactor for the enzyme methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. When B12 is deficient, methylmalonyl-CoA builds up and is converted to methylmalonic acid, raising its level. This marker is more specific for B12 deficiency than homocysteine, which can rise in both B12 and folate deficits; ferritin reflects iron stores, and cobalamin level measures the vitamin itself but does not always reflect functional deficiency.

Elevated methylmalonic acid indicates vitamin B12 deficiency because B12 is a cofactor for the enzyme methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. When B12 is deficient, methylmalonyl-CoA builds up and is converted to methylmalonic acid, raising its level. This marker is more specific for B12 deficiency than homocysteine, which can rise in both B12 and folate deficits; ferritin reflects iron stores, and cobalamin level measures the vitamin itself but does not always reflect functional deficiency.